If you have one or more channels open you can start making payments. When you joined a token network three channels were automatically opened with three nodes.
Let's walk through how to pay from the tokens screen.
Click the "PAY" button that has been made available for the token network you joined.
In the popup dialogue:
Enter the address of the receiver of your payment.
Select the token associated with the token network you're making the payment from. Note: The token is already pre-selected when you pay via the tokens screen.
Enter the amount you want to pay.
You can choose to fill in any number in the "Set payment identifier" dropdown for identifying your payment. If nothing is provided your payment identifier will default to a timestamp.
Click "Send" to complete your payment.