If you can have this professionally done. Cats have a lot of bacteria in the mouths and nails that can cause a bad infection. People have lost fingers due to cat bites. If you want to do it on your own buy a cat muzzle and wrap you cat in a large towel with just one foot sticking out. I would suggest using a file instead of nail clippers if you aren't experienced at trimming nails. You may accidentally cut too much off and cause your cat's nail to bleed. This is hard to stop. Buy septic powder to stop the bleeding before you try to trim the nails. Be sure to use a scissor type trimmer that is designed to cut the nails of cats.
wrapping the kitty up in a big towel like she is a burrito is a good idea. we do this at work for cats that aren't behaving, which is alot of them. you will need two people though. filing the nails may take a lot longer than your cat will be patient for though. trial and error will figure out what the best way is for your cat. if you can maybe just have the vet or groomer do it. it usually only costs 5 - 8 dollars to have them cut and save you alot of aggravation.
My cat usually lets me trim his nails every week. Because they really get long fast, and it reduces his urge to scratch my carpet. I usually use baby nail clippers and they work fine. I try and cut his nails when he is very calm, usually when he is just waking up from a cat nap. I try and do it as fast as possible, or one every hour.