The first time you have a recipe that calls for just egg yokes or egg whites, you panic. How do you separate the yoke from the whites? Really it is a pretty simple operation, it just takes a little practice.
To start, you need to get two bowls. One of them will be for the whites and the other for the yokes. Get out however many eggs your recipe calls for and place on the counter by your bowls. Taking one egg at a time, crack it on the counter.
Sidebar: You always want to crack your egg on the counter (or flat surface) and NOT the side of a bowl. Especially the bowl you are putting the egg into. Using the side of a bowl will many times lead to pieces of egg shell getting into what you don't want it in. It rarely happens when you use a flat surface. Back to separating eggs.
Using your thumbs, separate the shell into two halves making sure the yoke stays in one half. You need to be doing this above the bowl to be used for the egg whites. Now slowly transfer the yoke from one half to the other half while letting the egg whites release from the yoke and into the bowl below. You will never get all the whites to release and that is alright. When you have as such white released as you believe possible, place the yoke in the other bowl and repeat the process with remaining eggs.
If you find that you don't like separating eggs by hand, you can buy a piece of equipment. They do sell egg separators in many stores. Try my favorites Kohl's, Food Network and QVC to find one, if you must.
If your recipe is calling for both the whites and yokes but separated, continue with your recipe. If it only calls for one or the other, cover the part not needed and refrigerate up to a couple of days. If you have not used them by then, please toss them out. Remember that you can add them (either one) to scrambled eggs or omelets you make for another meal.
Now take the half you need for your recipe and continue with your cooking/baking.
Well was I right? It is a fairly easy process that just needs a little practice to feel comfortable. So get in there and separate some whites from the yokes.