If you haven't done it before then don't do it yourself... it can be fatal for your guitar... go to a local luthier or any guitar shop with technicians... See how they do it then you can do it yourself next time...
If your guitar has a truss rod, one that's adjustable, you can adjust it accordingly.... If it doesn't have one, you have to lower (or heighten) the bridge.... But mind you, both of these can lead to fret buzz if the strings are lowered too much (assuming you want to reduce the action of your guitar)...
@OP: Before you mess with your truss rod, check if your bridge saddles can be lowered. As rickkkyrich rightly pointed out, playing around with the truss rod can ruin your guitar if you have no prior experience.
