Everyone tells me to polish my caprass( i know the spelling's wrong i want to know how spell it right) or capbadge, but no one ever tells me how...? thnx!
Some badges - most, these days - are anodized and cannot be polished. Make sure yours is actually brass or a similar material that is actually able to take a shine.
Then go to the grocery store, or Walmart, and look in the cleaning supplies section and buy a can of BRASSO. It comes in a metal can. Here is a picture:

You can also use SILVO.
Shake the can well so the polish is well mixed. Put a dab onto your badge - use a drop cloth or newspaper, if you get this on the kitchen table, your bed, the floor - it will stain. This stuff is messy, and toxic.
Rub the stuff on your badge, then rub it off with a clean, soft cloth. Repeat several times, make sure it doesn't dry in the nooks and crannies or your badge will look crappy (dried brasso looks like dried toothpaste, very white and chalky). A good way of working the brasso is to use your finger, and keep moving the stuff around, then buff with the cloth. Your finger will get good and black. So will your polishing cloth. The black stuff is oxidation coming off the badge.
Oh, since you asked, it is properly called a Cap Badge, (some say Hat Badge also). A lot of people use the term "cap brass" or "hat brass" but these are incorrect; I think it is mainly in use by cadets.
There are more expensive metal polishes out there - Dura Glit, for example. If you want to cheat, go to a jeweller and have your badge chrome plated (for white metal badges) or gold plated (for brass or "yellow metal" badges).