Welcome to SolidWorks forums Matthew.
Do you have a standalone version OR network license. Did you keyed in a serial number while installing. If you've a network license then ask your VAR to get you the license file Or request it via customer portal on SolidWorks site. If you've standalone version then you need the register the product (you should see a pop up window to register the product).
This might be helpful: http://www.solidworks.in/sw/support/software-licensing-registration.htm
You might also find this post helpful for your future reference.