google "core strength exercises" and have a peek through the pages that come up.
Get a list of 7-10 exercises and pick three of them to try that you feel most suit you.
Please ease into them and only do as much as is easy for you. As you're just getting into it make sure you warm up and stretch and cool down afterwards. The first week is kinda just waking the muscles up, not working them out.
From personal experience, you don't want to overdo core muscles when getting back into, or, starting out on the workouts. you start to fear a sneeze or a cough.
