There is a couple of steps that need to be done for this. Visual Studio allows you to remotely push your app to a device (provided that both the PC and Surface are connected to the same network).
Basically you go here and download the Remote Tools for Visual Studio 2012 (near the bottom of the page) onto your Surface (remembering to download the ARM version).
You can then launch this program on your Surface.
Then in Visual Studio you can click the little drop down arrow next to the run button and choose "Remote Device". If both your development machin and your Surface are on the same network it should detect it automatically (but you may have to enter your Surface's IP address).
The first time the app is deployed onto the device the Surface will prompt you to get a developer certificate and once that has occurred it should just work.
This guide explains it far better then me and should give you all the information you need.
Goodluck!