You would go into the "SolidNetWork License Manager" on the machine you want to borrow on (found in the Windows Start menu) and go to the 'License Borrowing' tab. This tab will let you set a borrow expiration date and borrow one of the licenses to use off the network. The only real gotcha is that you have to have SOLIDWORKS closed when you do this otherwise the license will not successfully borrow.
You need to deactivate the license on the current computer,
This will release it back to the SW servers where you will be able to activate it from a different machine.