There should be two cables coming from that box and going to the engine, one will be throttle, one will be shift.
When you move the remote lever (the one on the box) forward or backwards it will engage the prop, you should feel a light stop point when the lever gets to that point, it usually only moves one inch or so before it is there. From that point forward it will begin to control throttle as you move the remote lever forward, or backwards depending on direction of travel.
One word to a new remote owner, when you shift it from neutral into forward or reverse, shift quick and smooth into either gear, do not shift slowly to that first position or you will hear a grinding/cluncking noise in your gear housing at the engine, this is the clutch dog trying to engage the gears. A smooth decisive shift into gear is MUCH easier on the gear case than slowly engaging it. Once in gear throttle up as needed. Also, NEVER rip your remote lever from running forward into reverse at any speed, come off of the throttle to neutral first, then go into reverse, never pull straight back through neutral without a pause, it may not damage it the first time you do it, but it will damage things eventually, or it may rip apart the first time. Don't chance it.
Bufford