You can edit your profile in Settings. Do not forget to click "Save" after writing your own introduction.
You can introduce yourself in the "Bio" field. MFM is available.
Include hashtags to let other users with similar preferences find you at "Trending Tags" at the Explore page.
Blue Bookmark icons next to "bot" are explained at Moderators.
"Cat" users have cat ears on their icons, badges "cat" next to their names, and 「な」(na) in notes are replaced with 「にゃ」(nya).
You can enable "Cat" in Settings. Remote users will see you as a "Cat" too.
Turn on "this account is a bot" in Account Settings to mark your account as a bot, an account whose actions are automated. Bots have "bot" badges next to their names and have a mark of robot at their user pages.
Other users including moderators and other bots tell bots from normal, unautomated accounts by this "bot" badge. Unautomated accounts should not mark themselves as bots since other bots might not reply/react to you. You may have seen endless reply chains between automated bots on Twitter.
Remote instances are also notified that an account is a bot. Some instances do not accept bots. In that case, your bot account are unable to interact with other accounts there.
Some Fediverse users put #nobot into their profiles to tell bots that they do not want to get follows/replies from them.
Each user has their own user page. Navigate to /@(username) (e.g. https://misskey.io/@ai).
User profiles of remote users usually inaccurate due to lack of synchronization between instances. Visit profiles on their instances directly to get accurate information.