Before you can begin to truly tension and adjust the tracking on your new band saw blade, you'll need to loosen the band saw guide blocks and rollers that keep the blade tracking properly. There are typically two sets of these guide blocks and rollers: one set is found in the sliding blade guard above the table, and the other set is found beneath the table.
Loosen the set screw that holds the block on either side of the blade on the sliding guard above the table. The blocks should slide freely left or right, either toward or away from the blade. Then, loosen the set screw and rotate the rear roller backwards, away from the rear of the blade.
Repeat the step for the set of blocks and roller underneath the table.