[Kevin Sevcik]

You have to dimension the angle, not just measure it. Also, you can only change dimensions in sketches. So first you should open up the sketch that pertains to whatever angle you're looking at. Dimension that angle, and then double click on the value to change it. If you get a message about overconstraining the sketch, it means you've added too many dimensions and they're inconsistent in some way. So then you need to delete a dimension you don't care about.