You have quite a few options. You can sign up with Google Music, (currently in beta) and sync your music to the cloud and it will be available on all your Google devices using the same credentials. You could also try plugging directly into your PC and using Explorer to transfer the files. Also there is an app called WiFi File Explorer that will allow you to do the same thing on your network.
Hi Roland, welcome to Android Tablets. Glad you became a member of the forum
Samba Filesharing can transfer things between your PC and your tablet using your wireless network. I usually just copy things from my PC to a micro SD card and then put the card into the tablet.
I normally use Bluetooth to transfer file, as well as card reader... I do not use an app for it anymore... anyways, it's nice to know that there's a more convenient way to do it. thanks @spider