These instructions may help you:
More Windows-centric, but more complicated, instructions here:
I believe you will find such instructions in the user guide that came with the TC. You will also find helpful information at the following:
A whole lot about Time Machine for help with TM problems. Also you can select Mac Help from the Finder's Help menu and search for "time machine" to locate articles on how to use TM. See also Mac 101- Time Machine.