On a Windows computer
This first method is probably best to use if you want to continue using
iTunes to manage your music collection, or if you consider yourself to
be a novice when it comes to technology.
- First, you need to download and install the Windows Phone app for Desktop.
- Click on Settings in the top right corner. (Alternatively, upon installation, the program may walk you through this process automatically the first time)
- Under Sync music, videos, and more from, select iTunes.
- Your music and other media will show up in the Windows Phone app for Desktop, allowing you to choose what to sync with your phone.
- Next, make sure Sync music has a check in the box next to it.
- Check the boxes next to the genres, bands, and/or albums that you want to sync with your phone
- Click the Sync button and watch the magic happen.
On a Mac
- First, download and install the Windows Phone app for Mac.
- Now connect your Windows phone to the computer.
- In the sidebar of the Windows Phone app, choose Music
- Choose what you would like to sync, then click Sync
Source: WindowsCentral