virus removal

Actually, you don't, but if you describe why you feel this way, someone may be able to assist.

Macs do not get viruses. You do not need any antivirus software. There is a difference between virus and malware/adware

You may find useful info and opinions in this thread:

i am new to Mac do i need antivirus software

Useful site that contains info about Mac threats: http://www.thesafemac.com/

Would you please specify why do you think you have a virus? If you see lot of ads or redirects on websites this may be the symptom of adware. Adware removal instructions:

https://support.apple.com/en-us/HT203987

You may also find adware removal guide on this page http://www.thesafemac.com/arg-identification/

If you do not want to remove adware manually use this anti malware tool in order to scan and remove it: https://www.malwarebytes.org/antimalware/mac/?utm_source=blog&utm_medium=social

If you see the warning in your browser or alert informing you about the virus - it is total scam.

1. Force Quit Safari .

Press command + option + esc keys together at the same time.

When Force Quit window appears, select Safari .
Press Force Quit button at the bottom of the window.

2. Relaunch Safari holding down the shift

Any such popup message will be a scam. Do not interact with such sites, or call any number presented.

Force quit Safari, then restart Safari while holding the shift key.

That may be coming from an adware infection of some kind. Download and run this perfectly safe and effective program, which will scan for and remove known adware.

https://www.malwarebytes.org/antimalware/mac/index.html

Did you install mackeeper application on your mac or you just see pop ups and ads in your browser?

If you've had the misfortune to install the dreaded MacKeeper this link should help with removal instructions:

http://applehelpwriter.com/2011/09/21/how-to-uninstall-mackeeper-malware/