how to add sata HDD to IBM Server

You will not be able to add the new drive to the existing array unless you delete and recreate the array incorporating the new drive. Alternatively, you can create a new array. You might need to get at least 1 extra hard drive so that the new array can support at least RAID1 or if your controller supports JBOD then you can add the single drive as is. Just keep in mind that ot will have no redundancy.

is there a way to add single not joined to any RAID ??

It all depends on your RAID controller. Most good RAID controllers in servers allow you to add a new HD to it and then expand the array on the fly. Depending on the OS you can then add the additional disk space as a new partition, or extend your current partitions to fill up the added space. Check the manual of your RAID controller for details. In some cases you need to add an optional battery to the controller to enable this function. Also that should be mentioned somewhere in the manuals. You should also be able to get the required info from the manufacturer (IBM).

Also, but again this depends on the RAID controller, you can often add a new HD and create a new RAID 0 array using just that single HD. To the OS it will then look like as if it was a simple HD.

got it
so it has to be linked to array it cannot be stand alone directly connected to the MB like the normal PC correct?