Open Steam on the computer you want to share from
Sign in to the Steam account that owns the games
Go to Steam
Select Settings
Open Family
Enable Library Sharing
Make sure Steam Guard is enabled on the owner account
Sign out of the owner account
Sign in to the other Steam account on the same computer
Authorize that account for sharing when prompted
On the other computer, sign in to the shared account
Open the Steam Library
Download and play the shared games that are available
Remember that only one person can use the shared library at a time
Remember that not all games support sharing