Posting in RMXP Tutorials was not only the wrong place, but it caused your thread to be moderated so no one could see it or help you. For your sake and ours, please be careful where you post threads. Thank you. Moved.
To take a screenshot, press Alt+Prt Scr, then open a graphics program like Paint or Photoshop, and paste it into a new image. Save it (preferably as a .png), upload it to an image host like Photobucket or ImageShack, and paste the BB code into your post.