Teach me how to download

Hi Leon.Welcome to the world of 'Help! What's happening now?"
The problem with downloading is that it means different things to different people. To some it is the act of pulling something off the internet to use on your computer, like a program or a photo or brochure, to some it's getting photographs off a camera and into the computer. to some it's buying music, apps, books, & videos from the itunes store or Amazon to use on your computer and to others it can be dowloading whole films from a torrent site.
In general terms it's the act of getting someing off a website and it's done in a number of ways. But it always starts (with a few exceptions) with you clicking a button on a website that says "download".If your mac is still set up as it came out of the box, then all downloads are automatically placed in a folder called "Downloads" which is located in your Home folder (the house folder with your name underneath) in the USERS folder. It should also be in your dock adjacent to the trash and also in the side-bar when you open a folder.
What you do with the download after you have received it depends on what it is.
If you buy something off the iTunes store or App store, then the computer will do everything for you after you commit to buying it and will sort everything out and put the file whereever it is meant to go.
I think it would be best if you can find someone to talk to so that you can see what to do - it's a lot easier than trying to follow my rambling!