1) Why would you want to? Serious question. RAID should only be used to address a specific need (or for the fun of it). What do you intend to accomplish by using RAID?
2) My first step would be to look for the manual on line. Do you have the manual? In most cases, where a separate RAID controller is not used, RAID is established in the BIOS and requires changing the disk-controller mode. This will make your system not boot.
3) "Merge?" If you already have data on the disks, you cannot RAID them unless you make a backup of the data. Putting two drives in RAID will wipe the data that is on them.
The most important thing in this post is the question I asked in point 1. What are you trying to accomplish?