Hi Debora, this is relatively easy but the precedure will vary depending on what you already have. If you have a hard solid copper line going to the faucet (no breaks/fittings) then you'll need to cut the pipe, and install a compression fitting. There's nothing difficult about this. If there is a threaded connection (i.e., a flexible hose connected to the copper pipe) then things even get easier. Explaining how to go about this is actually more difficult than the task (either scenario). Take a look at this link Shutoff Valve, and if you have further questions, just post back up!