When it is time for a creator to be paid, marked under "All Collabs" is a section called "Send Payments." Click Send Payment to pay creators. This will charge your card on file, and after processing, will be sent to the creator's PayPal.
Creators can also request a payment once their content is set live. This will automatically start processing a payment 7 days after the request is made, but if the agreement terms were not met, you can dispute the payment.