Going back to what Andy said - truss rod adjustments should be made slowly - never more than 1/4 turn at a time. Looking down the neck from the headstock, turn the truss rod to the right/clockwise to tighten the truss rod to reduce the amount of concave bow in the neck, and to the left/anticlockwise to loosen the truss rod and increase the amount of bow in the neck.

Too much tightening and you can put a convex curve into the neck, so that it's higher in the middle than at the ends. You don't want this, so be careful.

After any truss rod adjustment, make sure the strings are in tune and then check the result. If it looks good, then don't do anything else but wait for several hours - overnight if possible. The neck can take a while to settle down under a different truss rod tension, and may move a bit more over time. Once its steady and you have a good shallow curve, then proceed with the rest of the set-up.