To assign an IP from the IP pool to a vNIC on a VM, you can use the following lines of powershell:
$vm = Get-ScvirtualMachine -Name NameOfVM"
$staticIPPool = Get-SCStaticIPAddressPool -Name "IP Pool"
Grant-SCIPAddress -GrantToObjectType "VirtualNetworkAdapter" -GrantToObjectID $vm.VirtualNetworkAdapters[0].ID -StaticIPAddressPool $staticIPPool
Set-SCVirtualNetworkAdapter -VirtualNetworkAdapter $vm.VirtualNetworkAdapters[0] -IPv4AddressType static
make sure that the guest OS reflect this as well, and that you assign a static IP address that is alligned with the IP pool in VMM.
-kn