Modifying the Dock
The dock is a great location to place your most used applications and folders. Below is an example of what the dock on a Mac is:
The different icons on the left side of the dock are "applications." They are, in order from left to right, Finder, Microsoft Word, Microsoft Excel, Firefox, Google Chrome, and Safari. Then we have a divider with Terminal, System Preferences, and Preview. These applications are temporarily in the dock - when you open another application not permanently in the dock, it will take the spot of one of these three applications. Then we have another divider with the applications and downloads folders and the trash. Your dock will probably have different applications and folders on it.
Turning Hiding On or Off
"Hiding" is a dock option that, when enabled, will hide the dock from your screen unless you hover your mouse to its location. To enable or disable hiding, right click (or hold Control while left clicking) on the dock itself (not on an application), and select "Turn Hiding Off" or "Turn Hiding On".
Other Dock Preferences
The dock has many other options, such as the ability to show indicators for which applications you have open (a small dot below active applications), adjusting of magnification size, and position on screen. This and other options can be found in Dock Preferences, which you can access via System Preferences or by right clicking the dock and selecting "Dock Preferences…".
Add Items to the Dock
Add an Application to the Dock
First, open the application. Once the application is open you can right click (or hold Control while left clicking on the item on the dock). Then you should click "Options" and then "Keep in Dock." Make sure there is a check mark next to "Keep in Dock."
Now the application will remain on the dock even after it has been closed.
Add a Folder to the Dock
You might want to add a folder to the dock. Oftentimes you might even find the computer has some folders, like Applications and Downloads, already on the dock. Adding a folder to the dock is a simple process. Simply find the folder you wish to add to the dock and click and drag that folder to the space you want it on the dock. This folder will now always be easily accessible for you from anywhere on your computer. Note, this will not change the actual location of the folder, it just acts as a shortcut to the folder itself.
Remove Items from the Dock
If you wanted to remove something to the dock you could right click (or hold the Control key while left clicking). Then you would click "Options" and then "Remove from Dock."
Once you have clicked "Remove from Dock" the item will be removed from the dock as long as the application itself is not open on the computer. Take note that you cannot remove Finder or the Trash Bin from the dock. These instructions can also be used to remove a folder from the dock.