Dysphoria is, in this context, is the feeling of discomfort somone has due to the mismatch between their current body/experience and internal identity.
Euphoria is considered to be the opposite: a feeling of comfort, wholeness, and joy in someone's internal identity matching their external one.
Transition is the change (or changes) someone makes to allieviate dysphoria or have euphoria.
Not everyone experiences both euphoria and dysphoria - some report having only dysphoria or only euphoria.
And not everyone transitions the same - some transition a lot, some only a little, and some don't. Transition can be limited by social circumstances, financial reasons, technology not being yet available.
Ways People Transition and Alleivate Dysphoria
I'm no professional, but this is a list of things that might help if you are transID. Based on personal experience and those of others. This page is a bit barebones at the moment.
Stuff that Works Generally for Everyone
Expressing your identity and feelings through art
Using avatar makes like picrew.me to see how you are on the inside. If you are looking for an avatar maker on picrew that has specific options (like for species, disability, race) then try using a search engine if the in-site search doesn't give you results. There's also Doll Divine.
Having people that are supportive and understanding
Researching more about the thing you identify as
If dysphoric about skin - wearing clothing that covers it up so that you don't see it
Facial surgery (facial feminization/masculinization)
Other surgeries
Legal transition
Name change
Legal gender change
You can find more resources if you look for “how to connect to theriotype/kintype” on the internet. There's a big community for being transspecies and otherkin that doesn't consider itself a part of the transID umbrella.
Accessories
Tails
Ears
Fur-like clothing
Things to make you feel like you are in your environment
Room (or den) decor
Posters themed on environment (like forest/landscape posters)
Having furniture based on materials where you would live, like wooden furniture if you would live in a forest
Potted plants
Changing the lighting - dimmer or brighter
Going outside
Listening to ambience from your environment
Researching about your species
Quadrobics
Eating foods that your species eats (preferrably only if safe)
Research into what your species eats
Researching what foods are around where your species lives (plants, berries, fruit, prey animals)
Eating more/less meat
(I ask you to keep it safe for a human body though, wouldn't want to get sick from it)
Style changes
Dressing like the era you would ideally be from
In my perspective, more bright/warm colors look younger, more muted cool colors look older
Take note of what older/younger people wear and think about incorporating it into your style
Using different language
Calling “homework” “work” or vice versa
“I'm in school” feels more youthful than “Studying at XYZ Academy.”
More/less contractions changes the formality of language
Speaking more or less clearly can be associated with age
More or less big words
What language did people use when you would have been growing up?
Doing different activities
Coloring - adult coloring books are a thing now, but many people use coloring to feel younger
Playing with toys
Caring for / loving stuffed animals
Being a fan of more “childish” or “mature” media
Doing more or less “independent” activities
Cooking complex meals
Driving yourself
Making important decisions without the influence/help of others
Going places without a helper
Researching about desired culture/country
Learning the associated language and/or accent
Researching history
Traditions
Learning about the holidays
Trying new food, learning how to cook it
Clothing
Small things related to changing appearance
Tanning / trying to have less of a tan
Colored contact lenses
Dying hair
Some accessories can help with body parts feeling different or not having to see them.
Hands - gloves
Arms - armwarmers
Feet - socks, shoes
Legs - long socks, pants, legwear generally
You can get socks to the length of where the dysphoria is (like how there are thigh-length socks, knee-length ones, and calf-length ones)
Some socks and leggings have robot-themed patterns on them. This can help with the desire to have prosthetic limb(s). Some prosthetic limbs have patterns on them like leggings do.
Researching ways you might have learned to work around your desired abilities / Learning how to use the undesired ability less
Transblind
Covering eyes when possible
Learning how to navigate more with other senses
I believe there are screen readers for people to use
Transdeaf/HoH
Learning ASL
Turning off audio and turning on captions
Noise cancelling headphones / earplugs
Transmute
Learning how to use augmentative and alternative communication devices (AAC)
Speaking less when possible
Transcolorblind
Digital filters for screens
Surrounding yourself with less color (or less of the colors you don't want to see)