Drag the button that looks like a film strip (Media Manager) at the end of the row in the Available Buttons into the Current Editor Layout toolbar area.

The Media Manager will enable you to upload and insert various video and audio files, as well as assist in embedding Youtube and Vimeo content.

I installed Mediabox, but editor doesn't have a button.

JCE MediaBox is a standalone Joomla plugin for creating "lightbox" style popups in the front-end of your site - https://www.joomlacontenteditor.net/products/jce-mediabox