1. Look at the top right corner of the page
2. Click on your nickname
3. In the dropdown menu click 'Account details' - there you'll be able to edit the info. There is also an option to edit signature if that's what you also need. Signature is what is displayed below all your posts.
If you mean editing your profile cover -
1. go to your profile page by clicking on your username
2. Near your avatar find a button called 'Cover'
3. 'Modify cover image' will allow you to upload custom image. 'Style cover' will let you pick background color.