Sorry for the late reply.
1. Click the + in the bottom right corner
2. Type in the game's name in the 'title' box
3. Type in the game's version in the 'version' box(optional)
4. Click 'choose' and select the game's .exe file
5. Click the second 'choose' button, and select a image for the game(optional)
6. Click ADD at the bottom.
7. Click the newly added game to open it.