To create a Master Schedule, you need to go to the Master Schedule tab in the client profile.
If your agency user can't see that tab, it's because you need to activate access for your agency users. To do this, navigate to the Admin Settings>Role Management:
For each role that needs to see the Master Schedule tab, you will need to allow that access:
Scroll down to the client section and then allow full access (or read only) for the Visit Plan