I strongly recommend learning about partitions, as this will make installs
and reinstalls much less confusing for you. I started learning about them
when I was trained as a Windows technician but most of what I know now is
BTW In my other comment, I forgot to mention that you will also need "swap
partitions". A swap partition is a slice of the hard drive that is reserved
in case you run out of memory. I usually make Swap partitions the same size
as the amount of RAM on that computer.
You need a separate swap partition for each OS partition, although you can
usually shrink your ext4 partitions during install to make space for a Swap
partition. Sorry if this is all a bit confusing, but stick with it! Most of
us here have learned what we know by a combination of web searches, making
illuminating mistakes, and getting advice from people like the friendly and
helpful folks who frequent this forum.