After the guide blocks and rollers are out of the way, the next step to installing a band saw blade is to apply the proper amount of tension to the blade. Check to see that the blade is tracking properly in the center of the tires, then begin tightening the tensioning knob. While tightening the tension adjustment knob, rotate the top band saw wheel, all the while watching to see that the blade tracks in the center of the tire on the wheel.
If the blade is tracking too far forward or to the rear, locate the tracking adjustment knob in the back of the band saw's upper cabinet. Rotate the tracking knob slightly as you turn the wheel, and notice the difference in the centering of the blade. Keep adjusting the tracking knob until the blade rides perfectly centered on the tire. Keep in mind that a minor adjustment to the tracking knob can mean a huge difference in how the blade tracks on the tire, so make your adjustments to the tracking knob very subtle.
Once the blade is tracking properly, look on the back of the saw's upper cabinet for a tensioning gauge, such as the one shown in the image above. Adjust the tension on the blade until the gauge's indicator is positioned for the proper blade thickness. A wider blade will require more tension than a thinner blade, but the indicator should have appropriate marks for every popular blade size.
Once the blade is properly tensioned and tracking in the center of the tires, it is a good time to be sure that the band saw table is square to the blade. Place a combination square on the table, and align the opposite edge of the square with the side of the band saw blade. If the blade isn't perfectly square to the table, loosen the table adjustment knobs underneath the table, and adjust the angle of the table until it is square to the blade. Tighten the knobs to secure the table in position.
NOTE: There are tools such as a tensioning gauge to determine the proper tension on a band saw blade. If you need this level of precision on your blade, you may wish to consider investing in one. However, for general purposes, using the gauge on the back of the saw, along with paying close attention to the results of your cuts should be sufficient for most woodworkers.