I bought Chess of Blades Artbook DLC on Steam. How do I find the Artbook?

First, make sure the DLC is installed. Right click on Chess of Blades in the Library sidebar and click View Downloadable Content. Click on the Local Files tab and select Browse Local Files. Images of the process.

Help, I can’t access X’s route! Are there any walkthroughs or guides?

Heard there were some free wallpapers etc. Where might I find them?