How to do this?

updated my answer !

When I Select OpenERP Report Designer ‣ Server parameters, i am getting nothing and hence i cannot enter server details. Might be problem with openerp_report_designer.zip How to download this file? I download it from an external link.

i enter server url but what to write in port as online openerp has no port?

server XXX.my.openerp.com, port:8069, protocol: xml-rpc. This should work.

but its not connecting.. :(

Vardan, you should skip the "http://" while entering the URL. for eg: just put this as the server: 7-0-6633.runbot.openerp.com. I checked and it works fine

i entered url and port and its connected. After that its asking for username and password. When i am entering these details then its throwing invalid username/password error and i am entering right details.

There is no problem in connecting with server other than online openerp.

In OpenERP just go to that user whom you want to connect to the plugin in setting/users/users and change the password then try to connect.