Generally to clock a ported brake you have to chuck it in a lathe and cut the rear face until, when tightened, it screw on straight up and down (or with the ports horizontal). It's pretty easy to cut too much and have to go all the way around again. It helps to figure out how much 1 revolution is in thousandths, based on thread pitch, and then figure out how many degrees it's off from being on correctly. Always cut less than you think.
There are some that will also use crush washers if they have a pre-threaded barrel so they don't have to use a lathe or visit the gunsmith. The problem with that is they wear out and get looser. A set screw installed into the bottom is also another way to do it without a lathe or smith but I'd use a brass or aluminum screw so you don't damage the threads on the barrel.
BTW ported brakes with the ports angled back toward the shooter are generally the most effective but also the loudest.