The Key: Just Do It!
There are pointers here on filling in the very few fields needed to tell a story in its simplest form. We recommend always having an image. It helps communicate, of course, but also adds a compelling reason to look further in a way that flat text does not.
You'll find here instructions to add text and an supplemental page about adding images in screen shot versions.
There's, also, a video screencast version that covers both.
But don't worry much about the mechanics of how to post. If something seems unclear just take your best shot. We'll true everything up behind you.