what permissions level is marketpress.php supposed to be?

HI, I tried to upload marketpress.php and it said access denied. I tried 777 and it said

550 SITE CHMOD command failed.

: /wp-content/plugins/marketpress/0777 marketpress.php

If I change chmod do I have to do it for the higher level folder too ? And then do I have to reset it to back 644 after I upload my marketpress.php changes?