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

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

On lemdroid it is profile > credentials > delete account