Removing malware

I have been haaving issues with popups and ads that restrict me from accessing Google.  They state that I must update my software.  I just switches to Century Link and the tech verified that this is malware and a Trojan.  I thought that my AVG protected against this although it states my system is secure after an aall systems check.

Any suggestions on how to remove this before it gets worse or spreads?

Thank you!!!