It depends on the cat in my experience- i have some who will cooperate without putting up a fight and others who want blood if you even attempt to administer eye drops.
The best way i've found to give them is scruffing the cat by the nape of the neck with one hand- in doing so stretch the arm you're using to scruff with across the cats back to put a little pressure on them and hold them down. With the other hand (be sure you already have the top off of the drops so you can do it as quickly as possible) use one finger to pull the eyelid up a bit and then the rest of your hand to instill the drops. I normally at that point will put my hand over the eye and keep it closed for a few moments so that the eye drop stays in the eye and doesn't roll out.
If you get a really fiesty one though what you can do is scruff them (away from you so your head and their head is facing straight ahead) and gently lay part of your upper body on top of them (gently- but so they can't wiggle away) and then instill the eye drops with the other hand.