This is a quick walkthrough because Linux installers typically have a straightforward GUI. The hard part about installing a second operating system on a Mac or Windows device is the initial set up. Hard drives are broken up into partitions, which are sections of memory dedicated to specific tasks. For example, there is typically a partition for the operating system, and then you may have a ‘paging’ or ‘swap’ partition. Those ‘paging’ or ‘swap’ partitions are just sections of the hard drive meant to let your device hibernate safely, or free up RAM for more intensive tasks. These can also exist as “virtual partitions,” which just means a file is being used on the primary partition. Anyway, in order to dual-boot Windows and Linux or Mac and Linux you may need to partition your hard drive.
Typically you want to set aside at least 20 GB for a secondary installation of a Linux distribution. However, you may run into memory issues if you use your Linux distribution a lot and only allocate 20 GB. Therefore you need to consider what you intend to do and the recommended partition size. I am not super familiar with Macs, but they should have an application for managing hard drive partitions. Furthermore, on Mac after configuring your partition you will use Boot Camp for your installation; Boot Camp is software designed by Apple to make dual booting easier. On Windows, the software that handles hard drive partitions is Disk Manager.
The first step on Windows is to identify the largest partition, right click it, and select “Shrink Volume.” Now pay careful attention here because the units are in MB, not GB. That means for 20 GB you want 20,000 not 20. Then take note of the partition letter because that is where you are going to install Linux. From there, nowadays, it is a pretty straightforward process if you stick with a beginner friendly Linux distribution. Some beginner friendly Linux distributions are Mint, OpenSUSE, Fedora, and Ubuntu. I recommend Fedora, but the cool part about Linux is that there’s so many different flavors with their own pros and cons.
Lastly, if you are not super familiar with installing operating systems I do not recommend doing this on a primary device. When I first installed Debian on my PC it was on a PC with WIndows ME my neighbor was throwing away. I used an unprotected admin account in safe mode to gain entry, but I wanted to use Linux. Plus I found an unfinished paper on Abraham Lincoln, and I did not really want to accidentally snoop. I highly recommend utilizing every opportunity you get to improve though because it’s really paid off for me.