If your talking about your driveshaft working angles, then i have good and bad news. Good news, i can explain how to do it, Bad news, thats not the right tool.
To find working angles....
Put the car up on jackstands and in neutral, the key is the rear end needs to be jacked up until it is at ride height. Best way ive found to do this is to measure from a point on the rear end to the frame while the car is sitting on the ground, put it on stands, then with a jack under the rear end jack it up to what you measured. Then rotate the driveshaft until the pinion yoke is at 90 degrees, attach the tool pictured below to the u-joint and measure the angle. Then rotate the driveshaft until the driveshaft yoke is at 90 degrees and take that measurement. With the tool pictured below it is key to remove the u-joints retaining end clips if it is equiped with them so the tool will sit level and get an accurate reading.
The same measurements should be taken for the front driveshaft yoke and the rear trans yoke.
Next is the math....
If you subtract the rear driveshaft yoke angle from the rear pinion angle that will give you your rear u-joint working angle. Working angles should not exceed 4 degrees, same with the front for the front working angle. The front u joint and rear u joint working angle should be within .5 to 1 degrees of each other (GM Specs so they might be a little different).
Here are some pics from a GM training site as well as a picture of the tool
