Hello and welcome to the forum.
When I first started using linux,
I actually read some of the manuals.
Assuming you have linux installed or can boot it from a flash drive,
it depends on what you want to learn. Eg. open a shell (You may know it as Command Line Interface)
then type man bash There is about three and a half thousand lines in that manual.
If you had a word processor open Click on the help button.
Have a Great Day!