Here's a pic to help you set up your meter:
SPE-sp-152a.gif 72k .gif file
To set bias on each tube:
Insert the probes into the bias set points, holding them firmly in place. (red to +, black to-)
Insert the torx driver supplied with the amp into the hole for the bias pot, engaging the screw in there. Turn the screw VERY slowly to achieve the required bias setting. You will have to try each direction to see which way to turn it.
Read from the scale that goes to "250".
A reading of "100" would equal 1v, so you want to see a reading of "40".