How do you download game demos on ps3??

May be...

I try to click on the games and nothing happens??? Can anyone help??

turn the PS3 off and back on again (switch on back) the log back into PS Network go to store and try it again.

as long as you have a internet connection then all you need is to access the ps3 store and download what you want..

Once you're in the PSN store, you select the demo you want (using X on your controller). The screen should then change to one giving you a bit of a description of the game. There's a download button on there you then need to select.

The screen will go dark and you'll be given the choice of downloading now or in the background (or something along those lines, can't get to my PS3 at the mo to check)

Doing it in the background means you can do other things while you wait for it to download but it can take a lot longer.