You can edit an existing or create new virtual disk by using the VMware vSphere client. This is very helpful when needing to add space to an existing VMs disk or creating a new one altogether.
1. Log into vCenter or your stand alone ESXi host with the vSphere client:
2. Locate the VM you want to modify, and select Edit Settings:
3. You can see the existing virtual disks in the hardware list. Once highlighted, you can adjust the size of the VD. You can also see the disk type, the disks datastore location, and name of the actual VMDK file. From this screen you can also select Add… to add a new virtual disk: