osu! Forum

1. Download: https://s.ppy.sh/release/osume.exe
2. Create a new bottle in crossover for osu.
3. Stick the osume.exe file into ~/.cxoffice/your osu bottle/drive_c/Program Files/osu!/
4. Run osume.exe from crossover. Wait for it to update...
5. From crossover, go to Tools -> Run Command
6. In the "Use Bottle" dropdown, select your osu bottle
7. Beside the "Command" textbox, hit browse. Navigate to the directory you placed osume.exe in, and select"osu!.exe", then hit "open".
8. Click on Create Launcher, Select "Desktop", and hit "Create".
9. Click on "Run".
10. Restart crossover

There ya go!

You will also need to install needed dependencies.
I just used Dependency Bottle 64-bit_win10_Dependency archives from the unsupported application support link: https://www.codeweavers.com/support/wiki/mac/mactutorial/unsupported_deps

then followed the instructions provided above.