How do we screenshot?

[Kaykay]

I haven't been able to get steam to work inside ArtRage. The overlay doesn't come up with Shift Tab. And F12 doesn't take screenshots.
And when I try to upload a file of a screenshot I get a notice saying I must do it within ArtRage.
Yet I see many people have screenshots uploaded.

So how are people doing this?

[Yeoh-Sidhe]

http://steamcommunity.com/app/231180/discussions/0/864961722067500245/