The Windows PC app converts the BSB files into "qct" files. You should transfer these qct files to your mobile, not the BSB/KAP files.
Refer to the Android or iOS manual for help with copying maps.
The default folder for the converted files is C:\Users\USERNAME\AppData\Roaming\Memory-Map\qct. You may need to turn on "Hidden Items" in the Windows file explorer view menu to access this folder.
The same applies to Self-scanned maps (PNG/JPG/TIF), NV charts, or any other imported third-party maps.\