How can i edit a post in Showcase?

I am healily struggling to find how to edit the post i created in Showcase because a lot of images aren’t displayed correctly. So my presentation looks like garbage.

How can I edit it? (i need to edit the title also)

If i can’t, please delete teh post in order to let me create a clean one please.

Ah, I think it’s a problem of the post beeing too old.

CC. @Tom