Best bet is to upload the screenshot from in-game to the Trainz Gallery, then find it in the gallery, right-click and copy the image link, then paste it in your post by clicking on the icon to "Insert Image" and pasting the link there. I look forward to seeing your shot! If the image is in Google Drive you may have to put it in your Trainz - build number - screenshots folder, then go in-game and upload it from there.