alter role - superuser - permissions

I want to learn how to insert data into tables.
Using postgres 9.5.x on Fedora 24.

linux user account:  mmm
postgres database:  mmm
database mmm table: accounts

mmm=# \du
                             List of roles
 Role name |                   Attributes                   | Member of
-----------+------------------------------------------------+-----------
 mmm       | Superuser, Create DB                           | {}
 postgres  | Superuser, Create role, Create DB, Replication | {}


Tried to use the copy command to insert data from .csv file into table
named "accounts"

It appears I was successful in altering the role of user "mmm" and
making it a superuser.

But, when I try the copy command, the following error occurs:

mmm=# copy accounts
(employ_last,employ_first,service,website,userid,password) from
'/home/mmm/Documents/accounts-services.csv';
ERROR:  could not open file
"/home/mmm/Documents/accounts-services.csv" for reading: Permission
denied
mmm=#

If mmm is a superuser, and user mmm owns the mmm database,  the .csv
file is in mmm's home directory, what other permissions are required
or still incomplete?

Thank you for your help.

Best regards,

Mike