Hmmm. Looks like you can only submit news if you're an advertiser. From the FAQ: Who can submit a story for Hobby News? Due to the overwhelming number of news submissions, TMP currently only accepts news stories from our advertisers for the Hobby News section. (An exception is made for non-commercial announcements and stories of exceptional importance.) Non-advertisers are welcome to post announcements on our main forum.
So you'd post to one of the SF and Fantasy threads. You wouldn't get the big up front posting with a nice picture on the front page. But you could put a picture into your announcement.