You can change it yourself in one of two ways. First off, you need to know the right brace height, which is where the string is supposed to sit w/ bow uncocked. You get this by putting twists in your string, kinda by trial and error. my Excals have max and min marks scribed on top of the rail, but don't know about yours, a phone call should do it to Horton.

The first way to change/adj it is the he-man way. Stand the bow on stirrup, put which ever hand is strongest foot in stirrup and being careful to put no pressure on the stock or the rail, just grab the limb tip w/ strong side arm and pull up enough to get the string off limb tip. You kinda use your leg and arm muscles. The other limb tip needs to be on a piece of carpet or cardboard, as it will be trying to make a dent in the floor. The other way is to make a string changer like Excal sells for about $10. It just slides a couple of inches up the limbs and has a hole big enough to get end loops off and on w/ bow at about 25% of full cock. Good luck, it gets easier every time ya do it.