That's why on the download link, we provide a ling to the documentation :
http://wiki.ocsinventory-ng.org/index.php/Howtos:VMOcsinventory-ng
On Linux, by default, the profile root is associated with the password ocs. On Mysql, by default, the couple ocs/ocs is associated to the ocsweb database.
As there is nothing for ocsreports in this documentation you can try the official OCS documentation to get the generic password for ocsreports :
http://wiki.ocsinventory-ng.org/index.php/Documentation:Server#Configuring_management_server.
Just point your browser to the URL http://administration_server/ocsreports and login in with admin as user and admin as password.
I know : it's hard to read documentation :)