Q: how do I get rid of the pcassists.info malware now that I can't get to the Safari preferences?

The pcassists.info malware hijacked my Mac.  I made the mistake of clicking on the OK button that was in the window telling me to call 1 877 899-1824. I also restarted the Mac. Now I can't access the Safari preferences option to check how the settings have been changed. What do I do now to get rid of this plague?

I'm posting this on my old HP AMD Athlon laptop. HELP please !