When you say align the bandwheels, can you be more specific?
Are the wheels vibrating as they rotate? This means the wheels are not balanced and need to be machined and rebalanced. Cooks will do that if you need it.
Is the band slipping off the wheels? This means the crown of the wheel is incorrect and the crown needs to be re-machined. Again Cooks can do this.
Are bands breaking pre-maturely by vertical cracks in the gullet of the blade?
This means the band wheels are not co-planer and need to be brought into proper alignment. This is what I think you are asking about.
You probably have a drive wheel that is fixed on main bearings, and an idle wheel mounted on a sealed bearing on an axle attached to a hinged plate that can be adjusted using a bolt.
If so, find and loosen the locking bolt so that you can move the hinge with the setting bolt. Find a straight piece of steel or aluminum that you can lay across the width of both bandwheels horizontally. Lay it across both of them about 1/3 of the way above and again below the center axle. Check the outer and inner edges of each wheel. If the idle wheel does not align on the inner side, move the setting bolt in to allow the inner ilde wheel edge to move out and meet the steel straight edge. Reverse that if the outer edge of the idle wheel does not line up.
If both edges of the idle wheel won't line up with the drive side wheel. you may need to remove the wheel from the axle and reset it. On many mills there are 3 bolts that hold the wheel onto a cone shaped axle. There may be 3 holes between each of these bolts that allow for removing the wheel by inserting the bolts you just removed into them and driving them into the back of the axle mount and forcing the bandwheel to move oppositely, off of the coned axle. This will free it for re-setting on the axle. Pull the wheel all the way off, then remove the bolts and re-insert into their home. Tighten each bolt by hand until snug, then move to each bolt in succession and tighten 2-3 turns each in a round-robin fashion. Tighten each bolt to the exact same torque using a torque wrench. This should get the wheel onto the axle tightly and evenly. You may need to do both the drive-side and the idle-side wheels.
Then go back and re-check the plane of the wheels inner and outer edge above and below the axle. Again, adjust the hinge bolt to move the idle wheel into the same plane. When co-planer, lock it down with the locking bolt.
By doing this you allow the blade to remain in consistent tension as it moves around the wheels. This reduces metal fatigue over the life of the blade and should make the blades last longer.
Hope this is helpful.