There are two basic types of external bass knobs.
One is actually a bass booster, as in it artificially boosts a relatively narrow bandwidth. These are the bad types, as they will easily clip the amplifier. With this type of bass knob, you want to adjust your amp's gains with the knob disconnected. The bass knob can be thrown in the garbage can.
The other type of bass knob is the gain attenuation style. (I believe this is the type you were asking about Caleb, if I read you correctly) This type adjusts the amplifier's gain level, with its maximum setting being the maximum gain level you have set at the amp. Basically its a remote gain knob whose setting is capped by the setting you apply to the amp's on-board gain knob. These types are nice because they will not clip your amp, assuming you have the gains set correctly in the first place. With this type of knob, you can either set the amp's gain with the knob turned all the way up, or with it disconnected and then connect it once the gain is set.
I dont believe the OP has told us what amp he has, so we have no way of knowing what type of bass knob it is.are a guess.