1- First of all you will need to download a cracked version of Wallpaper Engine *Use whatever site you want* for example SteamUnlocked https://steamunlocked.net/47-wallpaper-engine-free-v7-download/
2- Install the program just like how you would install any program
now here is the important part how to download wallpapers for it from steam workshop.. Follow these instructions
1- Find a good wallpaper you like from here for example : we are using this one https://steamcommunity.com/workshop/browse/?appid=431960&browsesort=trend§ion=readytouseitems
2- now you will have to copy the link of the wallpaper you like and go on this site https://ggntw.com/steam
3- once you’re on the site paste the link and press Download
4- now after you download it extract it but leave it in its folder like that

5- now copy that file and go to wherever you installed wallpaper engine open the folder then go to Projects —> My Projects and paste it there
6- restart wallpaper engine and enjoy!