An easy way to get this is by going to System Preferences > Network on the computer in question, choosing Wi-Fi from the list on the left, and clicking on the Advanced button. So first, find the MAC address of the machine you want to set up time limits for. The basic idea is the same, but feel free to ask questions in the comments if you’ve got them. So let’s go over it, shall we? Note that these instructions assume you’re using Airport Utility version 6.0 under Lion, so if you have a previous iteration of the software, your steps are going to be a little different. For each computer, you can use its unique Wi-Fi MAC (Media Access Control) address to block it from the network pretty much whenever you feel like it, which is a big thing for conscientious parents who want to cut off Internet usage at certain times of day. If you’re using a network device from Apple (like a Time Capsule or an Airport Extreme), Airport Utility’s Timed Access Control setting is a pretty easy way to configure when the machines on your network are allowed to wirelessly connect to the Internet.
