1. Open a prompt.
2. Change to the correct directory where you want to change the permissions.
3. Change the permissions.
Assuming the step 3 is the hard one.
eg. to give owner of the file named foo a [r]ead,[w]rite and/or e[x]ecute permission, you can use command
To do the same thing for every file in the directory,
you can write:
To change permissions for the group or others (the ones not being the owner of the file or belonging to the group in question) instead, replace the u with g or o respectively.
To change the owner of the file, you can use the command chown to do it.
For more details see
and for example tutorial about unix permissions