Regarding Project Service Automation

I want to use Project Service for tracking my Project's Progress.

Actually I've created a project and assigned some resources to it. Now, I want to track my workers' performance on daily basis. Basically, I will have an estimated number of man hours for each project and Task within each project. Someone will show up and work hours for those Tasks in the Work Breakdown Structure and I want to add those hours for each Person (or Team) and track progress. I added some WBS tasks but wasn't able to add more than one resource for one task . Why?

I also want to know :

How Time Entries work for Individuals(contacts) and groups ? Since, we don't have field for selecting any resource in time entries.

Any help is welcomed.