This video shows how to use the two Photoshop actions to create two kinds of angle maps - swirling pattern (crop circles), or radial maps to create "pots" of grass expanding outwards. The two actions can be downloaded from here: support.nextlimit.com/display/tuts/Grass+Tutorials
If you want to find out more details about how angle maps work, watch Part 1 of the video.
An RGB angle map can be used with Maxwell Grass to have precise control over the direction of the grass blades. This tutorial will show you in detail how to create a few angle maps using Photoshop, including a map to create a crop circle effect.
If you're pressed for time or not interested in that much detail, watch Part 2 of the video to learn how to use two Photoshop actions which automatically create angle maps.