How do i install xbox live when i have a mac and a desktop?

i already have the wireless adapter and its hooked up to the back of my xbox but xbox live wont work. Our family computer is a desktop PC but my sister has a apple laptop and i think our internet runs off wifi. I need some help. Any ideas?How do i install xbox live when i have a mac and a desktop?
If you are using a wireless router and the encryption is enabled you will need the router encryption key code. You will use the key code when setting up the Xbox for wifi.How do i install xbox live when i have a mac and a desktop?
Xbox: unsure

Xbox 360:



Turn it on

Go to My Xbox tab

Go all the way right to the Settings

Go to Network

Configure

Scan For Networks

Pick Your Network

Enter password if applicable

Xbox Live

andys auto sport