Most Plugins used in WordPress may simply be updated by noticing the little red circle icon with a white number inside of it, denoting how many updates are ready and clicking on it. Some Plugins don't use the WordPress repository, so you have to manually install or update them which is normally a process like this:
- Download the .ZIP file to your computer
- In WordPress click on: Plugins> Add New
- Click on: Upload Plugin
- Click the button: Choose File
- Navigate your file system to find the .ZIP file
I love finding new ways to save time by using fewer mouse clicks, so what I do instead of steps 4 and 5 above, is to visually locate the recently downloaded ZIP file in my Google Chrome browser, then drag and drop the ZIP file from the status bar of the browser into WordPress, landing on top of the button: Choose File
There you go, save a few mouse clicks, be more efficient.