Click "Add Storage..."
Choose the new disk, and go.
If you are in a non-production environment you just :
- down the server
- put into the server the new disk
- start the server and make attention to controller BIOS utility to create LUN
- create the new LUN using the new disk
- start and connect with VI client to ESX
- follow the procedure described bottom to discover and format the new disk as VMFS