[Zubersoft]

If you already have a library on your Windows device that you want to preserve, then the fastest option is to use the library sync feature to merge your two libraries. On the phone, tap the three dots at the top right of the library screen, then "Sync Library->Synchronize to a device". Set the phone as the server, set the sync type to "two-way" (this ensures it merges without deleting anything) and then tap "Create Server". On the tablet, set it to Client and connect to the phone. You can backup your Windows library first to safeguard all your data just in case you don't like the outcome of the sync for some reason. I should mention that this will also update the phone to match the Windows device. If you don't want this, you can change the sync type to "Update Client", but change the merge behavior to "Only merge new songs and groups".

Mike