Yes, you can use any kind of oil you have available though I wouldn't recommend using any vegetable oil (like Crisco) b/c they are not healthy oils to ingest but olive oil or coconut oil will work great. Take up to a tablespoon into your mouth (less if you have a smaller mouth) but leave enough room to swish it for 20 minutes. You may need to spit some out as you go and as saliva builds up. Work up to 20 minutes if it seems like too much. Keep yourself busy doing other things so the time will go faster. There is no harm in going longer if you loose track of the time. Remember to breath and thing about the benefits you are receiving while you are doing it. That will make it more enjoyable.
There is a forum for OP if you do a search on this site. Also check out this site for more info - http://www.oilpulling.com.