Hi, my app does not work with Desktop Manager yet, but these steps work for me and my friends:
1. download my app
2. extract the archive and copy content to your BB device (e.g. SD card)
3. run the File Manager on your BB device and browse to the application files
4. Run MtGcounter.jad
5. choose Download
Now you can find the app in the Downloads folder, but you can move it to your home screen if you like.
Let us know if this helps.
I cannot promise, but I will try to add the Desktop Manager install files in near future.
Enjoy!