How do you read volts with a clamp multimeter?

I want to check the voltage on my power supply in my house. How do I check it using a clamp multimeter. Here’s a link to the same one I bought.
http://cgi.ebay.com/Digital-Multimeter-Electronic-Tester-AC-DC-CLAMP-Meter-/250747931088?pt=LH_DefaultDomain_0&hash=item3a61bdc9d0
Its a cheapo version and I don’t know how to use it. Its has 7 different options [...]