Here is a page that will help explain file permissions:

https://help.ubuntu.com/community/FilePermissionshttps://help.ubuntu.com/commun\
ity/FilePermissions>

First you will have to go to a terminal session then type

sudo <your username> then press enter. You will be prompted for your
password. Once you do that then you can use the commands chown to change
the owner (you) and chmod to change how you can access the files
(read/write). The above link talks about these commands and shows examples
on how to use them.

I hope this helps. It may not make sense at first but once you do it a few
times you will get the hang of it.