Custom HTML modules are a very useful feature in Joomla. You can insert any code you like from articles to photos to code. Here's a video explaining how it's done:

1. Login to your Adminstrator area.
2. Go to Extensions >> Module Manager.
3. Click on the "New" button.
4. Select "Custom HTML".
5. Enter your code and click "Save".

Video on Adding a Custom HTML Module in Joomla