Joomla is becoming pretty much the industry standard CMS for site construction. The team the develop it are reknowned throughout the world as one of the leading groups of open source database development. Joomla is a fantastic tool for any aspiring web developer and designer. Even the pro's use it.The reason why it MIGHT be a TAD slower to load is due to the modules, components and plugins designed by third parties. This is EXTREMELY marginal when compared to other CMS and it should not bother anyone that wishes to use it. Joomla is HIGHLY customisable and to answer the question that started this thread:
Goto your Joomla Administration area and select your EXTENSIONS:MODULE MANAGER Click NEW and then select CUSTOM HTML give your Mibew module a name and position your module from the POSITION dropdown list.
Scroll to the bottom of the page and inside your editor select the "HTML" button within your tools tabs across the top of the editor window, a window will appear, here is where you PASTE your Mibew code copied from your Mibew installation. Close this window, publish your module and then preview it on your website.
IMPORTANT: Don't forget to select what article/page you would like this module to appear, select ALL or select meu then click on the article/page you wish your module to show within the MENU ASSIGNMENT pane above the editor within your module edit area. Any problems just message me.
Hope this helps.