I'm assuming you are talking about the dewclaws. Normally these are the easiest to trim. But if you have never trimed nails before it's best to go to the Vet, and ask how it's done.

Most dogs will react to toe nail clipping in a negative way. It probably causes discomfort in that the nail is usually pulled a little during clipping. I've always tried to make it sort of a game with mine. After clipping 1 or 2 nails I stop to give em a treat. They eventually come to associate nail clipping not only with slight discomfort, but also with ... treats!