Both programs are very user friendly and easy to use. You can download them both for free from CNET:
Download the files and install them (very easy). To run Ad-Aware, click on "Scan Now" which you'll see on the left hand side when you open the program. It'll ask you to select the scan mode, and I usually just let it use the default scanning options. Click Next, and it might take 30 minutes to scan your entire harddrive. When it is finished, you'll see a list of all the spyware entries that it found on your PC. if you right-click on one of the checkboxes, you should have an option to "select all." You should see a button to click that will either Finish/Clean (I can't remember off the top of my head). And that's how you use Ad-Aware.
When I've run Spybot, I've noticed that it picks up different types of spyware than Ad-Aware does. To run the program, open it, and click "Search and Destroy" on the lefthand side. You'll see a button at the bottom that says "check for problems." Click it, and it will scan your PC (it's a really fast scan), and then list all of the entries it finds. Some of the entries will be already checked off (the registry entries are usually not checked off by default). I always select all of the entries (it makes a backup just in case, so you can always undo the changes), and then click "Fix Selected Problems". and that's it.
I hope this all made sense lol.