Only hard part is getting the wire thru the hole on the other end. Once you get the wire thru I will bend a 90* on the bottom bring the wire around and tie it off on the back side. Once there I pinch the top 1a and bottom 1b (pics in second attachment) together slightly keeping the wire tight and bring the wire around the top and tie it off. You can see on the back side how the wire is tied off on the tabs. You have to open those tabs up a small amount and once you have the wire tied on the first take a pliers and pinch it down to tighten on the wire slightly. The reason for pinching the frame is once the wire is tied off the wire will be tight. That is one key when replacing it.
I looked at my wire stock and the packages for the guitar strings I use says 9 and the other package say 10 on the front of the package. Here is what I use.
