To make a folder or file available offline in Windows 7, navigate to the folder and right click the folder or file and then click Always Available Offline
It’ll load for a few seconds or minutes depending on the size. Now you’ll be able to access it while you aren’t connected to the network. When selecting the file or folder in explorer you can see in the status bar the state. It should says: “Always available”
To see all your offline files go to the Control Panel -> Sync Center -> Offline Files
Further reading at Microsoft How-to