How to install Team Fortress 2 Classic (2016)
How to install Team Fortress 2 Classic
Step by step:
Download the client.
Once downloaded, extract everything to your "steamapps/sourcemods" directory. You should now have "steamapps/sourcemods/tf2classic".
Install Source SDK Base
Go to the 'Tools' section in your Steam client and Install Source SDK 2013 Base Multiplayer.
After it's installed, right click it and select Properties, then click the Betas tab and choose "beta_test".
Close the properties and it should begin updating.
Once it has finished updating, restart Steam
Check your games. You should see "Team Fortress 2 Classic" has appeared on your games library.