You're using a rogue DNS service, the purpose of which is to circumvent restrictions on copyrighted content. That service is not to be trusted.
Please back up all data.
Unlock the Network preference pane, if necessary, by clicking the lock icon in the lower left corner and entering your password.
Cllck Advanced and select the TCP/IP tab in the sheet that drops down. Near the top, you'll most likely see this:
Configure IPv4: Using DHCP
If that's not what you see, stop here and ask for instructions.
Otherwise, select the DNS tab and delete all the DNS Servers from the list on the left by selecting them and clicking the minus-sign button below. Click OK, then Apply.
Select the DNS tab again. The server list should have been automatically repopulated with at least one address, and you should have normal Internet access. If so, you can close the preference pane.
If the server list is empty, go back to the TCP/IP tab and click
Renew DHCP Lease
Check the DNS server list again. If it's still empty, click the plus-sign button and enter this:
8.8.8.8
That's Google DNS, which I don't recommend for more than temporary use. Click OK, then Apply, and ask for instructions.