How to Add Extra HDD to an Existing HP DL 380 G9 Server

Dear All,

Greetings!! 

We have an HP DL 380 G9 Server with 5 SAS 10K HDD on ADG 6 (01 HDD on HotSpare) with WIN2K16 Hyper-V Installed and 3 Business Critical VM's Running on them.

I need to add an additional 3 HDD  (SAS 10K) to the Server without disturbing the current status.  i.e. (Don't want to break Windows or RAID or Loose Data)

Can anyone point me in the right direction with involved steps.

Appreciate your Assistance Very much

Thank you

Cheers