You're going to select the field they are currently placed under, be it contributor, requesting invite, etc., and check the box next to their name. Then you choose the level you wish to make them from the drop down menu, and click "Change Level".
"See, that's why they call them 'sick' days, cause you'll be doing something SICK!" - Bishop
"Pffft pffft pffft! I'm no fucking two planker." - shibby
"FUCK YOU WITH A BURNING MARSHMALLOW STICK." - aja_kiki in a little tiff of rage haha