Create a shortcut to steam-idle.exe,
Right click it, change the properties of the shortcut
Add the AppId of the game you want to idle to the end of the target line

Or run steam-idle.exe from the command line with the appid on the end

You can get the appid from the steam store url of the game in question.

Note: if you've had all of the card drop for a game then running the game further will not give additional card drops, steam gives you roughly half a badge once per game per account (excludes free games).

You can create the short cut to steam-idle.exe. Or as I have the Idlemaster Estended ( v1.4) When you open the program, you click in the File window, then you click in settings.
It depends on the version, but as I said, with version 1.4 in the idling behaivor section you will have the fast mode option selected by default, you must select the box that says idle each game individually.

Now the program will idle each game individually, in A-Z order.... but in real time, one minute during the idle master is working is a real minute in the game.