Trying to add array to ESXi VM, 'select' grayed out

I'm totally new to VM.  Have a new HP server with two raid arrays and 20 cores.

Have created two VM's, both using disk storage from Array1.  Need to add Array2 space to SQL server vm, however when I edit and try to add existing array the 'select' button is grayed out.

Also, next week we'll be getting server# two, an identical HP server for Exchange - how do I add the new server to the first ESXi

I like what I've seen so far

Dunbar