Assuming that you're using a browser, click on your username, go to setting, click on Delete.

If you're on an app, I can't help. They are all different.

you cannot delete your account, you are bound to us all forever muahahaha

On lemdroid it is profile > credentials > delete account

lemdro.id uses an alternative frontend, but you can access the default at l.lemdro.id and then perform whatever actions are needed as usual