your syntax is incorrect. proper usage of the chmod command is:
chmod [+/-]drwx file or directory name


what it seems you want however, is to add that user to a group that has the rights to edit these files.
so, say you have a file access_log, this file has the premissions set to: -rw-r--r--
the owner of this file is nobody, and lets just say the group is httpd. so you could chmod +w access_log to add write privelages to users in the group assigned to that file. then you add your user to that group, httpd.