Apple TV (3rd generation) - Manual (Page 18)

18 Chapter 2 Configure.
To set up Home Sharing in iTunes:
1 Open iTunes on your computer.
2 Choose Advanced > Turn On Home Sharing.
3 Enter your Apple ID and password, and then click Create Home Share.
4 Repeat steps 1 through 3 on each computer you want to use for Home Sharing.
For information about iTunes, open iTunes and choose Help > iTunes Help.
To set up Home Sharing on Apple TV:
1 On Apple TV, choose Settings > Computers.
2 Choose Turn On Home Sharing, and then enter the same Apple ID and password
you entered on your computer.