You can make your own thread, describing the situation on scam accusations board, preferably with format as shown on this thread, as it'll help people understand the issue and key facts at glance. The button to create a new thread will be on the upper right side of the board, labeled "new topic".

You can upload the supporting evidences [screenshots of conversation, email, and the likes] through talkimg, it's a image hosting service provided by one of the prominent member of this forum. As you're still in newbie rank, images won't show on your post by default unless you buy a copper membership or ranked up. But don't worry much about image visibility, someone will quote those images for you and make it visible.