Create a Ledger
Ledgers are the equivalent to channels on Hyperledger Fabric.
You can have a Network with 10 organizations but segment multiple Ledger for different groups of organizations (org1 to org10 in the "public" ledger, 1-2-3-4-5 in a ledger, 1-3-5-7-9 in another ledger) that way data and smart contracts can be segmented.
To create a new ledger, go to your Network.
And click "New".
Fill the form and select which of the existing Network's participants you'd like to include. It could be all of the current participants, or just some.