Open Steam and sign in to the account that owns the games
Click Steam in the top-left corner
Select Settings
Go to Family
Enable Family Library Sharing
Select the device and the account you want to share with
Authorize the computer
Have the other person sign in to their Steam account on the same device
Download and play the shared games from their library
Make sure the game is not restricted from sharing
Make sure the owner is not using the same game at the same time if the game does not allow it
Repeat the authorization process on each device you want to share from