Extract the content of the downloaded ZIP file and copy the stylesheet.mod directory into your BlitzMax\mod\MaxGUI.mod\ folder.
Compile the module with the following command:
C:\Blitzmax#> bin\bmk makemods -a maxgui.stylesheet
C:\Blitzmax#> bin\bmk makemods -a -h maxgui.stylesheet
Examples are located in the stylesheet.mod\examples folder, but to use this module in your own application you need to add it at the top of your project like this:
import maxGUI.drivers
import MaxGUI.stylesheet