Grim, consider it sort of like an eyepatch. Easiest mathod is to roughly make an estimation of how big your eye socket is. Make a small puddle on a plate, feather out the edges so it is thin and dry it with a hairdryer. Dust it with talc (blush brush) as it is peeled up so it won't stick to itself.
If you estimated well, it will fit fine over your eye, (down to your "eyesack," up to your eyebrow, into the side of your nose, and just past the outside corner of your eye.) If it doesn't fit yet, trim it down with scissors. The thinner your latex edges, the better it will blend with your skin.
You can then CAREFULLY outline where the edges will be with adhesive. PLEASE Be careful not to let any adhesive drip in your eye. Notice I didn't need to put adhesive on my eyelid. Press the eyepatch into the edges and press inward so it cups in. let dry, then add whatever gore you like.
tips: stipple with more latex and make-up to give "pores." Blood can hide flaws if needed.
As for latex not coming off so fast, there's lots of different answers to that, but a simple one is try washing and drying your face first so oils are "stripped" from the skin. Then stipple on the latex as opposed to smearing it on. It tends to grab more that way and gives nice pores and divits.
