The first Sections shows you some Basic Infos about your Account and let's you set a Profile Image that will be shown on your public profile.
The second Section offers you the Option of changing your Account Password. Just enter your Old Password as well as your new Password as stated in the Form and click the Change Password Button.
The Callsign Section shows you all Callsigns that are attached to your Account. You can add multiple Callsigns to your Account, so there is no need for multiple Accounts. You should add your Callsign to your Account so that you can attach it to your logbooks, that is very important if you want to use some external services like Clublog.
To add a Callsgn you just click the Add Callsign Button to open the Dialog, enter you Call and hit the Save Button.
Only enter Callsigns that you Own!