First go to Target.com, then search Cartwheel in the search box, like shown here
Then it will take you to the page to sign up and create an account. Once you have done this you can add offers you want.
Then pull out your handy dandy smart phone and go to the app store. Once you download the cartwheel app, you can just sign in and see the offers you have already chosen and even choose new ones on your phone. It will total your saving for you. Here is a screen shot of my Cartwheel and all the savings I have had to date!