what do i do now?

[apu]

when i run diagnostic i get the following response:
Plans error:
Calendars file data/calendars.xml not found!
New calendars file data/pending_actions.xml not found!
Events file data/events.xml not found!


Diagnostic information:
Script Name:plans.cgi

Warning: The email reminders data file: data/email_reminders.xml is not writable. This will cause some email functions to be disabled or not work correctly.
Warning: The calendars data file: data/calendars.xml is not writable. The add/edit calendars tab won't appear unless this file is writable.
Warning: The pending actions data file: data/pending_actions.xml is not writable. The add/edit calendars tab won't appear unless this file is writable.
Warning: The events data file: data/events.xml is not writable. The add/edit events tab won't appear unless this file is writable.
Plans version: 7.5.5
Perl version: 5.6.1
Debug info:
unable to open file theme/plans_lang.js
unable to open file theme/plans_lang.js for writing!

i've set permissions (not sure if correct permissions for all xml files and .js file.
help would be appreciated as i'm not a programmer nor do i know perl.
thanks for all and any help.