After purchase the game will be available for download in the list of your past purchases
The rest is answered in the support FAQ
Is there a limit on how many times I can download or unlock a game I bought?
You can download the game as many times as you want. There is a limit on the number of times you can unlock, but the limit is so high you'll probably never encounter it. (The limit is simply there to prevent serial numbers from being posted to the web where hundreds or thousands of people can access it.) On the rare chance that you do use up your game activations, just email our friendly support staff and we'll be happy to increase it for you.
You can also install it on multiple computers at the same time.
I am a Community Moderator, and I am here to keep the Forum a fun place for everyone.
My posts represent my personal opinion. I am a volunteer, not a TTG employee.