In your Beamer dashboard go to Notifications by clicking on the menu at your left.
Look in the feed for the post you want to move. In the top right corner of the post, click on the edit icon.
You can then change the order of the post by just changing the date. Click on the date on the top left corner of the editing screen and select another date.
After you’re finished you can save as a draft or save and publish right away.