Make sure it is checked / enabled after it finishes downloading.You might see a download progress bar in the list item if it takes a while to download. Return to the game, and you should see the mod listed in the Workshop mods list. Browse items in the workshop, and when you see a mod that you like, click on the 'Subscribe' button. The Steam overlay will open and show the Workshop.You should see a 'Browse Steam Workshop' button on top of the second list.Run the game while Steam is running, and open the Mods menu from the main menu.Instructions for installing mods through the Steam Workshop: