You need Lux installed on both machines.

Start Lux on the Master machine (where DS is installed) and let the scene start rendering.

Goto the 2nd machine (the slave) and assuming it is Win7, click on Start Luxrender Slave in the Luxrender program group.

This will open a window and in this window will be an IP address, take a note of it.

Goto your master PC and in the Network Tab and in the Server field, type in the IP address of the slave.

Press the + button and you should see session details appear in the list. If not, check the Lux log.

Once you are happy that network rendering is happening, I would change the Update Interval in the Network Tab to 1800 (30 minutes) as a minimum.