Photoshop Elements 8 HELP?!!?!?

Hi, I have a Wacom Bamboo pen and touch tablet with PSE8. I can't figure out how to get pressure sensitivity. I had it set on there before, but I accidently messed it up and now I can't figure out how to get it on there again. I keep going to that little drop-down arrow at the top next to the airbrush looking thingy and i get a menu that has check-boxes for Size, Opacity, Hue jitter, Scatter, and Roundess, and that still isn't working....please help me!!!