What parts of the account do you need to change?

To add a Bio to your profile, click on your name in the upper right section of the screen (on desktop; I don't know what the site looks like on mobile) and click "Edit Profile." This should give you a few other options as well. To create a custom profile picture, you'll need to host the image on another site, like Imgur or Photobucket, and link to it in your "Edit Profile" section.

You can change your name once every thirty days, but if you make a mistake, you can message paarthurnax (the site admin) to ask for another name change.

You can also check the Site FAQs for more information.

Hope that helps!