Where to start the Config?

Hi Experts,

i started learning SAP HR. I clearly undertood the concepts? now i have started config? now my question is where to statt config?

1.Do i need to create Enterprise Structure First, then org structure?

2. and when to switch the integartion switch between OM and PA?

3. How to move the organization structure along with positions?

Can some one expalin me the process flow? or direct me to the source where i can find answers for all of my questions?