Friends were on a web site to see how to hook up a zip line for their pond. There was a link that was suppose to show a part they needed. When they clicked on it a woman dancing on a pole came up. They exited right away but now all that shows up when they try to start their computer is something that wants them to spend $100.00 or more for antivirus. I have told them not to give out any information as that is a scam but is there a way to get into their computer to fix the problem or set it to a previous date?
That is what’s known as a ransomware attack. Lockscreen ransomware locks your screen and asks that you pay for to have it fixed. You’re correct that your friends should not give out any information. This is a scam.
The best way to defend against ransomware is to keep your security and virus protection software up-to-date and only open attachments from trusted sources.
If your Windows computer is hijacked by ransomware, Microsoft suggests two ways to remove the infection. The first way is to restart your computer in safe mode  and run the Microsoft Security Scanner. After completing the scan, restart your computer.
If that doesn’t work, you’ll need access to another non-infected computer that has access to the Internet. You can download a copy of Windows Defender Offline here  and follow the instructions on how to create a bootable device . Then boot your infected computer from that device.
It’s a complicated process, so the best thing to do is make sure you don’t get infected in the first place. Make sure you install security software and keep your definitions up-to-date.
If that doesn’t help, your friends will need to to contact a legitimate company where they live and have a professional take care of the problem.