The Steam-Client also has a built-in way to take screen-shots of games you're playing at the time, it's the F12 key by default. Then after you close the game, go to your profile, and you should see a "Screenshots" link you can click on to access & manage them.
If you then click on a picture to enlarge it, you'll see it open up full-size in a new windows, and a url/link along the top you could then copy & paste if you want to post it in a forum perhaps to let others see. Example;
http://cloud.steampowered.com/ugc/54290 ... F60573A7E/ That's a screen-shot on my Steam-profile, taken from my Western Wildwood route.
You may need to have your Steam-profile set to Public though if you want others to be able to see it.
Or, you could upload some of your images to some photo-sharing site, such as make yourself a free account at
http://photobucket.com/ , then upload your images, then you can copy & paste the link to your image, example;
http://i1231.photobucket.com/albums/ee5 ... HD_032.jpg ,or for some forums (like RWA here), you can put the image-url into the Img code, and have it appear on your post, like this:


(Screenshots from my King's Arm Highway Deluxe route,
http://www.rryard.com/kings_arm_deluxe.html ,at the Shipyard area)
Cheers! :)