Paratech2008: Thanks but How do I deselect or select without clicking?
I didn't select anything?
Ok, I looked it up.
My bad - nothing is pre-selected, so you can't de-select anything.
Now to your question:
you select the game(s) which you want to buy, by left clicking into the checkbox to the right of the game's name.
If you want to check out a game's store page before you choose, simply right click on that game's name and open a new tab.
The game you already own can't be selected, because it features no checkbox.
Once you selected at least one game, you can click on the button "redeem" at the bottom of the coupon.
That button takes you to the check out area.
Hope this helps.