Kaspars

Metronet AS

Plugin adds a meta box to every post, page and custom post type where users with editor capabilities can promote other users (with author or contributor capabilities, by default) as editors of that post.
Plugin provides the following filters:
<ul>
<li><code>custom_editors_enable_roles</code> — Specify an array of user roles which should be allowed to be promoted as editors of specific posts and pages. The default is: <code>array( 'contributor', 'author' )</code>.</li>
</ul>
A plugin by <a href="http://metronet.no" rel="nofollow ugc">Metronet</a>.

Multiple Editors

Allow multiple editors and contributors per post or page. Also enable contributors and authors to upload files and add new pages by default.

Md Abul Bashar

Just Allow Media files Upload access for Contributor users role.
Just Install then it’s worked. don’t need any more step. If you want then you can see documentations with screenshot <a href="http://www.codingbank.com/contributor-media-files-upload-access-wordpress-plugin" rel="nofollow ugc">Contributor Media Files Upload Access</a>

Contributor Media Files Upload Access

Just Allow Media files Upload access for Contributor users role.

Multiple Editors vs Contributor Media Files Upload Access