There is some confusion on this game as it doesn’t show up in your Steam library as it is “Free to Play.” To add to your account, click on “Play” for base game, then “download” for each DLC. Cancel out of the installs unless you want the 15gig install now. To verify they are linked to your account: 1) Click on your login name in upper right of screen 2) Click “account details” 3) Click “view licences.” You should see them added to your account but won’t be listed in library until installed. Return to the game page will show “In Library.”
Click on base game then click on the 3 free dlc on the page.
https://store.steampowered.com/app/436180/Raiders_of_the_Broken_Planet/