1) On your mybubble Overview page, on the right side, click on "Edit your public profile".
2) On the subsequent page, again on the right, click on "Edit your profile".
3) You will now see a large header on the left that says, "Edit Your Profile".
4) Click into the large textbox, and put your cursor in front of the top line. On Windows. Hit your "enter" key on your keyboard to make some space at the top. On a Mac, you have a "return" key, instead.
5) Now paste the code that you have copied from the code box, above, for the banner, at the top of that textbox.
6) Scroll down to the base of the page and click the "Save Changes" button. You're done!
7) Scroll back to the top right, where you see your own name and the logout button. Click your name to view your updated profile.
The banner is only 350 pixels wide, and will look like this on your page, after you paste the code: