The HP Server should have come with a SmartStart CD/DVD that you can boot the server off of and configure the RAID controller. If it didn’t, you can download it from the HP support site.
(Thanks Jmm-irl for reminding me of the SmartStart name. I couldn’t remember it for the life of me.)
on boot up hit F8 at the ORCA prompt, this starts ORCA (Onboard Raid Configuration Adminstration), its a simple tool that allows you to create basic raid arrays. if you have clean disks and want a raid 5 just insert all you disks and boot ,ORCA will automatically place disks into an array, if two disks are present it will put them in a raid 1 if more than 2 disks then a raid 5.
smartstart is downloadable from HP version 8.15 now and comes with array configuration utility (ACU) for more complex arrays and setting such as Selective storage presentation, changing block sizing etc.
hope this helps