However,I am not able to configure this device to access Internet.
I'm not even sure SmartAX MT841 ADSL works under Linux (did you Google for it?) (but as is it recognized, it might) - but the usual question for this at helpdesks would be: What have you tried?
Have you tried GNOME PPP? - And where, in your experience, are the points of failure?
(I mean, I might not be able to help in a technical sense, but maybe, in a logical sense...)