Hi Rose welcome to the forum!
I have been playing with polymer clay since last Oct. One of the best resources available to us is www.glassatic.com try searching there for what you need. I have tumbled my pc beads. There are a few different options. This one seems to work the best.
1) Find a plastic place mat that you can cut up.
2) cut it to fit inside the barrel of your tumbler
3) glue/staple 1000 wet/dry sandpaper to the plastic place matte - if u glue let glue dry following directions on glue container
4) put sandpaper strip in the barrel, add water and a tiny drop of dish soap
5) tumble for 24 hours or more depending on what you want to achieve, if you have applied pearl ex or something else on the surface this will remove some surface treatments, you also need to consider bead shape, some shapes will tumble better then others
6) experiement and see what works for you
7) after tumbling a good buffing with a light touch will give you a nice shine.
Good luck and have fun
Vanessa