This forum thread answered my question about giving access to usrs, but it didn't tell how to give that access to the users. To do this:

Open the instance in SSMS.

Open the "Security" folder and then the "Logins" folder.

Right-Click on the user name and choose properties. If the user is not listed then you will have to add a "New Login".

Click on the "User Mappings" option.

Check the box next to the msdb database under "Users mapped to this login".

Add the user login name under "User" and add the "Default Schema" (eg: dbo).

Check the box next to the appropriate role under "Database role membership for: msdb".

Click "OK" and the user will have that permission for the Job Activity Monitor.