Fixing a forward bow is usually pretty straightforward. The problem here is that your truss rod is too loose and isn’t exerting enough pressure against the neck, and the strings are having their way and pulling the neck forward. In this case, you’ll want to tighten your truss rod to increase its resistance to the force exerted by the strings.
Now it’s time for the actual adjustment. Use a hex key or socket wrench to do this.
1. First, if you have a truss rod cover, you’ll want to remove it with a screwdriver.
2. Now, tighten the truss rod using your hex key or socket wrench by turning it a quarter turn or so, clockwise. (A guitar’s truss rod is usually accessible through the sound hole or at the head of the guitar). If the nut is to tight and hard to turn, you should abort this mission before you snap the rod. You’ve most likely ran out of threads. You can take the nut off and add a washer or two, (this will give you a few more turns). If that’s not enough, you have a serious problem and should see a luthier.
Continue steps 1 and 2 until the forward bow in your neck is gone.
Now you’ll want to do one last check to make sure you didn’t tighten your truss rod too much. (This would cause a back bow). Carry out one last “physical assessment,” as detailed in the previous step to make sure you’ve removed any forward bow from the guitar’s neck.
Okay, last step. Do one more visual assessment of your neck to be sure you’ve completely eliminated any forward bow and haven’t caused any other neck problems. If you don’t see any signs of other problems then you’re done with this part of the setup. Give yourself a pat on the back. Refasten your truss rod cover to your guitar.
Now you’re done adjusting your neck. You can continue the setup, but some luthiers suggest letting the neck rest over night before continuing the setup. This will allow the neck to settle in it’s new tension position before continuing a setup.