Hi Eli, and welcome to the site!
Pick one (or more) Linux distributions to download from
here on our site or from
DistroWatch. As I mentioned above, some good distros for beginners are Ubuntu, Linux Mint, and Zorin (and Linux Lite is good too)... but there are many other choices available. The file you download will be a .iso file, and you need to use a special method (burn image) to burn the file to a DVD, or you can use some special software to burn the .iso file to a USB flash drive. There are many free programs to burn the Linux .iso to USB, and I'm sure you can find some of them with Google.
Once you get the Linux burned to DVD or USB, you can boot directly on those and use Linux in a "live" session so that you don't do any harm to your Windows or Mac computer. Or you can install another free program called
VirtualBox that will let your install Linux in a special environment called a "virtual machine." This also will not harm your regular Windows or Mac operating system.
Those are the most common ways to get started. If you have a spare computer that you can erase, you can also do a full Linux installation. The best way to do that is to let Linux have the whole computer and erase Windows, if it's there. There are ways to run install Linux and keep Windows, but that is more complicated for beginners, and you are really at risk of messing up Windows... so you may not want to go that way unless you are comfortable re-installing Windows if things go wrong.
If you have more trouble or need more advice, please start a new thread in one of the forums and ask questions as specifically as you can so we can focus better on your problem. Good luck!