1. Article Manager
The "pages" on your site are referred to as articles, the main content for each page. One of the first things you always want to do when creating a new page on your Joomla website is create a new article. Content Management Systems work by controlling how your site handles information, so it is natural that this should be your first step.
2. Menu Manager
When you work with menu items, you must remember that these are just links that tell your site which article it is pointing to. Menu items help you assign modules to specific pages, rather than having to show them on every page or none at all.
3. Module Manager
Modules can be anything form pictures to text, forms or any kind of info you would need contained in a box that can be moved around to various sections of the website. A module allows you to share more info on your site's pages without putting everything in the main content section.
A module, for the most part, is a program to create content that surrounds your “main content” section. These are mainly displayed in the different module positions: top, left, right, etc. Joomla! modules usually go hand-in-hand to display certain information from other installed components. Ex: display latest forum post made on your forum component, display random images from your image gallery component, display latest news, most popular articles, so on and so on. Even the menus are modules. Note: You can display modules in “main content”, but that’s another how-to.
4. Plugin Manager
Joomla! plugins enable you to execute code in response to certain events, either Joomla! core events or custom events that are triggered from your own code. This is a powerful way of extending the basic Joomla! functionality.
Prior to Joomla! 1.5 plugins were known as mambots. Mambots were able to change content only and were based on certain signal words. Since then their scope has been stretched and extended to such an extent that to enhance the meaning of the new functionality the developers decided to change the name from mambots to plugins. Joomla! 1.5 includes legacy support for Joomla! 1.0 mambots.
5. User Manager
If you want to make some changes on your new site and add new content on it and you don't want the content to be seen by anybody, here are some things you can do. You can assign an access level to that page temporarily, so that only registered users can see certain pages. Whenever the new content can be shown to everybody else, you can set the access level to public. This way everybody will be able to see your updated content. You can do that in the menu item manager.
6. Global Checkin
Sometimes, if more people work on the site, you can get locked out of a certain module or article because the site thinks someone else is still editing that item. That is very common and it is not a big deal. You just have to go in the administrative side of your site and hover over the "Tools" menu item and select "Global Check In." Now Joomla! knows exactly what is being edited and if that article or section was locking you out before, but not really being modified, Joomla! will unlock it so you can get back to business.
7. Joomla! Components
A component is an extension that enhances the core functionality of your Joomla! CMS. This is usually displayed in the “main content” section of your website. Think forum, image gallery, contacts. So on and so on.
These 7 simple tips from above will definitely help you familiarize with your new website. If you have troubles with dealing with all this, you just have to get back to your web design company.