1. Go to BitcoinACKs.com

2. Find a pull request that you want to sponsor and click its Pledge ฿ button

3. Sign in to GitHub

4. Authorize the OAuth

5. Decide how many satoshis you want to pledge and hit save

6. Done! The total amount pledged has increased

7. When you're satisfied with a code review, go to Bounties Payable, click the Reviewers drop-down, and select the reviewer you would like to pay. (Pay the author too while you're in there! Both roles are a lot of work!)

8. You'll be redirected to the developer's BTCPay Server

9. Send the sats!

That's it, you're done!