1. Extract the downloaded file (glyphicons.zip)
2. Copy the "glyphicons" folder to "ckeditor/plugins/" folder
3. Open the file "ckeditor/config.js"
4. Add theses lines:
	config.extraPlugins = 'glyphicons';
	config.contentsCss = 'path/to/your/bootstrap.css';
	config.allowedContent = true; 
5. In your HTML's <head> section add this code:
	<script>CKEDITOR.dtd.$removeEmpty['span'] = false;</script>
6. Make sure to clear your browser's cache
7. Done