Adding game pictures takes permission, to keep out spam. If you'd like to contribute, contact site staff and ask.
With permission, open a game's page, choose "Your options" and then "Add pictures of this game". Each picture needs alt text (a short description for readers who can't see it), and you can add a caption and a credit. Pictures from members may wait for a staff check before they show.
Once they're up, anyone writing about the game can use them in reviews. Please note that we do not accept images that are watermarked for use on other sites, or that are owned by other entities. You should generate your own screenshots, or post images obtained from official sources, like online press kits.