How to install multiple S-ATA drives ??

Greetings!

I am new to this S-ATA stuff.

Running an ASUS P5LD2-VM. Two S-ATA sockets on MB - one labelled S-ATA 1-3 and the other labelled S-ATA 2-4.

I installed a single S-ATA drive (my bootable XPdrive), and plugged it into the 1-3 SATA socket and it was recognised as Third Primary Master.

1. Why the Third?

How do I get it to be recognised as FIRST Master?

2. I should be able to install four S-ATA drives on this MB - how do I do that? Do I need a "splitter" of some kind to install more than two S-ATA drives?

Thanks!

Doc