As I have said before I am a super left brainer. So I am fond of jigs and story poles and measuring sticks. I find the position for the hole I will use for the screw eye or D ring by measuring with what ever I have handy that's about the right size,. Here I am using a wire cutters. I will do the same thing on the other side. I want that hole about a third the way down from the top. I make a nice hole with my awl. I just push it by hand down into the frame, you don't need to hit it with a hammer! You are going to either screw the D ring to the frame with this hole or turn a screw eye into it. Both go much more easily if you mark, and then start the hole with an awl.
You can see that I am working on my fitting table with the frame face down onto the mattress pad I have there to protect its front. I always put the picture on the table with its top towards me. If I don't, sometimes I will put the wire on, and then when I turn the picture over the wire is across the bottom and not the top of the frame. I make a point of having protocols for a lot of things, if I always do them the same way, and in the same order I screw them up less often.
There is the little D Ring , but you could use a screw eye too. That works just as well. Both D rings and srew eyes come in a variety of different sizes for different weights of paintings.
Here is the address of United, a company that sells D rings and about a zillion other items for the framing industry. I haven't placed an order with them in a long time. They sell things in large quantitys. It takes a while to go through a thousand D rings.
Here are a couple of spools of picture wire. The one in front is a plastic coated medium weight wire. The spool in back holds a braided wire, that is rated for a heavier painting. I got that from Jerrys Artrarama. You have to be careful with picture wire, it is easy to cut or poke your fingers with the stuff. I have done that many times and then bled on the frame.
Pull the wire through the ring or screw eye. Now WATCH CLOSELY! the next part is important.
You need to loop the wire and send it through the screw eye a second time! This will keep it from slipping. Here is another shot of that.
Pull it tight, and then you are on to the next step.Twist about 6 inches of wire around the the hanging wire like so.
Now go to the other side and repeat the process. From now on you will carry the painting by the wire as much as you can. Every time you put your acid laden thumb on the front and center of the top rail of a frame, you wear away a little more of the finish. Try to keep your hands off the fronts of your frames. Let the interns at the galleries ruin em.