First of all, plug your phone into your computer using a USB cable.
1. Open your documents
2. Open your music library
3. Under 'My Music' go to your iTunes folder
4. Open the folder iTunes media
5. Open the folder music
6. In here, you will see folders of the artists from your iTunes library. Click on the desired one.
7. This will bring you to folders of the albums written by the artist you chose in step 5, click the one you want.
8. Here will be a list of songs with icons that look like white pieces of paper with a blue music note on them.
9. From here, you'll have to look to the left side of the window under 'computer'. This will be a list of hard drives and other devices in/connected to your computer. One should be the name of your phone or something noticeably similar.How Transfer Music from Android to iTunes
10. Pick the desired song and drag it over the hard drive of your phone listed in step
11. From here the song will automatically sinc to your phone's music library.
You can also following step to How to Transfer Music from iPod to iTunes