You can have up to 10 lines of notes stored with your profile (finger). These notes may be used for pretty much anything you want. E.g. you could pose a riddle, or post the standings of a tournament you're running, or just say a little about yourself. (Max 330 characters per note.)
To set your profile go to the menu above in BlitzIn and click on Edit. From the list choose 'Settings' and now you can click on the 'Profile' tab.
Or: Use the keyboard combination Ctrl + S
This brings up your Settings window. Click on the Profile tab.