Filling out W4 for multiple jobs

My partner works 2 full-time jobs and is a high earner, and we do not understand how to fill out his W4 form so he can take out the appropriate amount. He files as single with no dependents. How do we use the online calculator in this scenario to understand how much he needs to take out, and how do we fill out the new (more complicated) form to address the "multiple jobs worksheet" section?