First, hire a web admin and have 5k$ cash on-hand. Then go the company tab and create the network, which should enable the tab. You may need to rest after that to refresh the interface but going in/out of the studio also works to force a refresh. It's recommended to have a PA for online operations as well before you start camshows but I can't recall if it's a strict requirement.
If you're really strapped for cash, you can have a staffer temporarily change to be a web admin for that first step and then switch them back again afterwards. But you're going to suffer frequent outages and reputation hits if you don't have enough IT staff to manage your servers.
It's amazing how close to real life this game is sometimes...