That sounds like the version of iOS you have, which is one update behind. I would recommend updating your phone, and also downloading any updates for the Weebly app.
In the newest version of the app, tap on "Website" on the bottom, then tap on the blog card, then tap the + button to make a post. When you've added the content you want to add, tap "done" instead of "post". This will give you the option to save the draft.
