I am not sure if you can update your profile much in the application. I do know that you can update your email address and change your password and display picture. Anything besides that, I think you have to get on a computer and modify other things. To change your password/display picture or update your email, pull out the side bar where it has tabs (portal, notifications, subscribed, unread, etc.) and at the top (with the tabs showing) there should be a profile icon next to the back icon and setting icon. It looks like a person's head- tap on that and it should take you to your profile. From there, you can tap on your current pic or the camera icon to add a new display pic. to change password and update email, at the top should be a menu icon (looks like 3 vertical dots on my phone), click it and it gives you those two options. I did just find that you can add a signature if you go back and click on your settings icon. You can change what mode you are in (light or dark), font size, notifications, and things like that. If you scroll all the way to the bottom, you can tap on "signature" and select none, "sent from ___" or you can customize it.
Welcome to AA! I hope that helps some!