How do I activate the internet?

From the menu, I select the relevant "internet" icon, but I get the message:
"failed to connect to the internet. Go to http:https://www.opera.com/help?version=4.4" with your desktop browser or contact your service provider for internet settings.

I have a connection from both my mobile provider and my home provider.
However, I don't know how to activate it on mobile.

Could you please guide me?

Thank you !