Unwanted messages from Antivirus McAfee

I was searching for a website earlier today on google, clicked what was listed as the company's website. A new page automatically opened but was NOT the company's website and I then may have accidentally clicked on something without thinking and now I am getting all these messages coming in every 30 seconds on the top right side of my MacBook saying "Turn on your McAfee, click here to run antivirus" or "Your McAfee has expired, click here to renew". Please tell me there is a way of getting rid of these. Thanks.