First I will describe a simple conveyor. We have 1 idler roller
which is free turning and fixed into position with no adjustments.
Then 1 power roller which moves the belt and has adjustments on
both sides of the roller.
The initial setup would be to adjust the power roller towards
the idler roller as far as possible. Install the belt so that it is
centered as possible. Adjust the power roller away from the idler
roller as evenly as possible to get enough tension on the belt that
the power roller will drive it.
The next step will be to track the belt. The object is to adjust
the power roller so that the belt stays centered. Turn on the
power. If the belt goes to the right side of the conveyor, adjust
the left side adjustment back towards the idler roller until it
centers and stabilizes, or vice versa.