Yes, you can connect multiple ad accounts from one network.
Step 1: Click on the profile icon in the bottom left-hand corner and select Accounts.
Step 2: To add another account, click the Connect button above the Accounts table.
Step 3: Select a network.
Step 4: From there enter your credentials, accept permissions, then select which accounts you'd like to bring into AdStage.
Step 5: Your account will now be going through its initial sync. Find more details on initial syncs here.