in case you haven't figured it out yet.
1. click "Type here to search"
2. type in %appdata% exactly
click on the first result.
this will send you to This PC>Local Disk>Users>(your pcs name, it will be different if you changed it)AppData>Roaming.
Click AppData at the top, next to Roaming.
Then click Local
Scroll down until you see PizzaTower_GM2
Click PizzaTower_GM2
click Levels
BAM there are all your levels you made and downloaded