Find your name and stock image (sometimes called an "avatar" at the top right of your screen)
Click on the small drop-down arrow to the right of the image
Click on "My profile"
In the Administration block on the left hand side, click on "Edit profile"
Modify any of the text boxes that you wish to complete; keep scrolling down the page for more options. (Note: you may have to open up the other areas - e.g. "Preferences" area - by clicking on the little side arrow next to the title of the section.)
When you are finished making all your changes, click on "Update profile" at the bottom (it's a blue button)
