Here is a link that explains the Linux directory hierarchy.
You may be able to right click on a file and then change the permissions graphically. ( I don't use Linux Mint. )
The chmod command isn't difficult. There are three sets of permissions. The User, Group, and all Others. There are three fundamental permissions, Read, Write and Execute. The Execute bit needs to be set to run a program. For directories, the Execute but is used to enable you to enter the directory.
Some examples are:
chmod u+rw file
chmod ug+rwx file
chmod o=rwx directory
The "+" plus sign is what you use to turn on a permission bit. The "-" sign is what you would use to turn off a particular permission bit. The "=" will assign the permission bits you indicate exactly, clearing any you didn't select.
I find it easier to read a nicer formatted man page:
man chmod -t | kghostview -
If you don't have kghostview, try a different postscript viewer. The -t option will produce a print quality postscript version of the man page(s). I find this version easier to read. If you used kde, you could enter "man:chmod" in the konqueror web browser. This may work as well for info pages: "info:chmod".