HP ProLiant ML570 G4 - Adding a new disk to the Array

Hi

Wonder if anyone could give me some quick advice with this, we have an old ML570 G4 which has 3 146GB disks configured in a Raid 5 array.

My colleague just added a 300GB disk to the server and I want to expand the array. I loaded smartstart and got this screen attached, what options do I need to click to expand the array so it includes the new disk? I have never done this before and worried about wiping the disks entirely.

Kind regards,
Mark