Once you have purchased this DLC, you can access it as follows:
1. Click "Manage my DLC" in the DLC block on the game page in the Steam client.
2. Check the "Install" box next to "Vivid Days - Walkthrough"
3. The DLC will be downloaded to your games folder that you set up for Steam. The file is called "Vivid_Days_Walkthrough.pdf"
Default path: "C:\Program Files (x86)\Steam\steamapps\common\Vivid Days"