If you look really closely at the photo you provided, you will see a wire that is attached from the bottom of the corner post
to the top of the brace(2nd) post. It is behind the woven fence wire. Notice how it makes an "X" pattern. Now, here is how you make that wire brace(assuming the metal brace is already installed with lag screws, and no woven fence wire is installed yet.)
You start with two fence staples, one gets pounded in at the bottom on the corner post opposite the metal brace lag screw(like where one would hang the pivot for a gate). Only pound the staple 1/2 way into the post. This will hold the bottom loop of the #9 wire for the "X" pattern. Now, the 2nd staple goes on the brace post, up high and on the opposite side from the metal brace lag screw. This will support the upper loop of the #9 wire around the back side of the post. Note: I recommend you put the staples at the same height as the lag screws of the "other post", this makes the final "X" pattern look better. Next, unravel about 20 feet of #9 wire(don't cut yet) and make a big oval loop thru each staple and around each post. The area where you want the two wire ends to cross is at the middle of the metal brace.(middle of the "X"). You need about 10" of overlap(each wire) to make your tie(20" total). Cut wire. This is where you will tied the #9 wire together. Tied it as tight as you can by hand as you loop each wire wire end back on itself and twist.(the tie looks like two eyelet bolts hooked together). It should look like an "X" pattern with one wire on the South side of the brace and your tie should be on the North side of the brace with the connection right in the middle. The next part works better with two people. One person will be on their knees next to the wire loop by the corner post, the other person will be standing by the wire loop closer to the brace post. Each person needs a tool or item to twist with(about 12-16" long). We use the handles of two large cresent wrenches, some poeple use sticks, rebar, the claw of a hammer,etc. Next, with both people on the same side of the fence, each one will stick your choosen tool inbetween the wires halfway between their post and the metal brace. This is where the twisting(tightening)of the wire loop will begin. Important note: One person must pull the top of his tool TOWARDS himself while the other person pushs the top of his tool AWAY from himself. Try to rotate an equal number times for each person until the wire is taut. The wire will break if you go too much, then remove your tools.
This is hard to explain explain on paper, but I tried.
