Can't extrude walls on floorplan

Hi, I am new to sketchup, and am loving it. I created a floorplan but am unable to select the walls to extrude them. If anyone could help, I would really appreciate it! Thanks!

momsPad.skp (204.3 KB)

You should start from here: Sketchup Fundamentals


Ahh, that helped a ton. Thanks so much!