Click on Posts on the sidebar to view all the posts for Media page
These posts are listed by published date. So if you want to re-arrange the posts, simply change the publish dates of the posts.
Add new Media post
Click on Add New button next to Posts heading
Fill out all the fields, upload a post image then click Publish or Update
Unpublish or delete a post
Click on Move to Trash link in Publish panel to delete a post
Click on Edit link next to Status: Published and change the status to Draft to unpublish it.
Click Update under Publish panel to save the changes
Change the published date
In Publish panel, click on Edit next to the Published date and set the date as you like.
Click Update to save the changes.
Change the number of posts displayed on 1 page
Hover over Settings on sidebar and select Reading
Change the post number to whichever you like and click Save changes
*Do not change the setting of everything else.