The user control panel is located up there in the top right under your username (next to Private Messages)
Here are some screen shots of some of the Board Preferences that you can modify
Popular things that you can change include
font size
maybe you want different font sizes between mobile and your desk top?
style preferences
which notifications you receive - do you want in PM or email?
maybe you don't want any PM?
maybe you don't want email from anyone?
maybe you don't want anyone to know if you are on line?
maybe you don't like the 'Recent Posts' on the index page?