you should start by planning how much storage you like,
and how much storage you are willing to sacrifice for durability
the best practice is to use Raid 5 – you will need to sacrifice only 1 hd
and will get a decent recovery option when one of your hd will fail.
to start your NAS in easyNAS is simple:
1. create a filesystem with your HDs
2. create a volume
3. create a shred dir