To determine the exposure of the AB using the 358, attach the AB sync cord to the AB, then the other side into the connection on the front right side of the 358.
Press the mode button on the meter, then turn the big wheel to Flash Mode on the meter (3rd icon on the top, IIRC) Release the mode button and turn the big wheel again to set the shutter speed you want. (Make sure you don't go higher than the camera's max sync speed, she said, smacking her head
Press the measure button on the side, the flash will fire, then the meter will indicate your f/stop. Set the shutter speed and f/stop as indicated on the meter, on your camera in manual mode. Connect the sync cord to the camera/AB then fire away-your exposure should be correct.
When I first started I always checked the exposure after making any adjustments to the AB. It's a good starting point, and you can always fine tune by reading your histo.
(Also, make sure your ISO is the same in camera as well as on the meter- indoors generally I set it at 100).
The averaging mode in the 358 is great when you're ready to use the 2nd AB for fill, but that's another post:)
Hope I got this right, it's been a while. The transmitter/PW receiver combo is a good addition for when you want to trigger the flash(es) remotely.
kl