Once you've created a network, you can assign programs to it by following the steps below.
Assigning programs to a network if you have organization-level user-access
1) If you have organization-level user-access, you can manage all networks at omnystudio.com/settings/networks
2) From here, you can click 'Assign new program' for the network you'd like to add a program to.
3) Select the program or programs you'd like to add and click save!
Assigning a program to a network as a program-level user
1) Go to program details for the program you wish to add to a network and select an existing network from the network drop-down.
2) Click save and repeat for every program you wish to add to a network within your organisation.
Note: it's important that you group your networks carefully because the analytics for the combined programs will begin accumulating for that network as soon as they are set/added. Learn more about network analytics here.