Currently, there is a known issue where users are unable to install the DLC when selecting the "Download" button from within the game.
This "Download" button will be removed in a future update.
Make sure that you close the game app before installing/uninstalling the DLC.
Make sure to also wait until the install/uninstall is complete before launching the game app.
The list of DLCs that are available will vary depending on which regional version of the game you own. The screenshot displayed in these instructions are based on the European regional version. The details can be found in the DLC section of your Steam Client.
If you were unable to download using the method below, then uncheck all DLCs and go to the Downloads tab located in the Steam Settings, run the "Clear Download Cache" option near the bottom, and try redownloading them individually. Having several DLCs selected at the same time could cause issues when downloading.
Go to your Library from within the Steam Client and select "METAL GEAR SOLID MASTER COLLECTION Vol.1 BONUS CONTENT"
Right click and select "Properties"
Go to the DLC section, select the DLC that you would like to install, and deselect the ones you don't want to install.
This setting can be changed at any point in time.
