For changing permissions/attributes of files/directories you don't need to open them.
How did you upload files to server? Through any FTP manager? Now you only need to go to installation directory of affiliate software
and mark these files and directories for which you want to change permissions.
Next steps depends on FTP manager you are using:
In Total Commander you have to go to menu (F10) > Change attributes
In FlashFXP you have to right click on files and from rolout menu choose "attributes (CHMOD)"
and then change permissions to 777
If you do not want to allow such permissions, you can do it another was. Only webuser(apache) and cron have to be able to write to the files... so if you will set this at your apache, then you can set any other permissions to the /accounts directory and its files.