This post shows how to use WYSIWYG text editor TinyMCE 4.1 in a Rails 4 application:

https://gist.github.com/maxivak/8e64ed8c0d86b0d994e1.

TinyMCE WYSIWYG text editor comes with a MoxieManager file manager  which is not free.

File manager is needed to insert an image by selecting from images on server or uploading a new image to server.

elFinder is an open-source file manager. In order to use file manager with a Rails application, we need a backend (connector) – phallstrom/el_finder gem.

Read all details on  github:

Install TinyMCE editor 4 with Elfinder file manager in Rails 4 app.