How to define new project calendar

Summary:

I have the following situation:

We have a customer that wants to have his billing on a 4-4-5 weeks schedule, thus we would need to have set up this kind of billing cycle.

Based on what we read so far, we would need to define a new project calendar with this 4-4-5 weeks pattern.

I have created a new project schedule and when trying to assign the new schedule to the project created in Project Management, my new schedule is not found. Are there any additional steps that shall be done in order for us to be able to see the project schedule in Project Management?