Installing the official Android File Transfer app on a Mac will allow you to connect an Android device and transfer files. When connected, you can browse your Android files just like any other folder on your Mac. You can also transfer music files from your iTunes library to your Android device.
Steps
Part 1 of 3: Install Android File Transfer

Step 1. Click the Safari button on the Mac

Step 2. Visit android.com/filetransfer/

Step 3. Click the "Download Now" button

Step 4. Click the androidfiletransfer.dmg file under "Downloads"

Step 5. Drag the Android File Transfer to the "Applications" folder
Part 2 of 3: Transfer files

Step 1. Connect the Android device to the Mac via USB

Step 2. Unlock the Android screen
You will have to keep it unlocked to access the files.

Step 3. Swipe down to open the Android "Notification Panel"

Step 4. Press the USB option in the "Notification Panel"

Step 5. Press "File Transfer" or "MTP"

Step 6. Click on the "Go" menu and select "Applications."

Step 7. Double click on "Android File Transfer"
Android File Transfer can start automatically when you connect the Android device.

Step 8. Click and drag the files to transfer them
When Android storage appears, you can browse and move files just like you would any other folder on your computer. File size is limited to 4GB when moved to or from Android device.
Part 3 of 3: Add iTunes Music to Android Device

Step 1. Click the iTunes button on the Mac
You can find it in the Dock.

Step 2. Right click on one of the songs you want to transfer
If you don't have the right mouse button, hold down Ctrl and click.

Step 3. Select "Show in Finder"

Step 4. Highlight all the music files that you want to transfer
You can select individual files or entire folders.

Step 5. Drag the selected files to the Android File Transfer window

Step 6. Drop the files into the "Music" folder

Step 7. Wait for the files to transfer

Step 8. Disconnect the Android device

Step 9. Press the "Music" application on the Android device
The application will vary depending on the Android device you have.
