How do I remove adware and malware from my IMAC?

One option that has a very good reputation: Free Antivirus Replacement & Anti-Malware Tool | Malwarebytes

I did have the Adware saying 3 viruses. I clicked off and now my desktop screen is full of icons saying unknown download on all of them. I must have done something twice because now they are double stacked. I don't seem to have the malware anymore but the icons are still there. I'm afraid to do anything except drag them all to trash and then empty trash.

Once removed protect yourself:

Effective defenses against malware and other threats