Windows Updates
Making sure your software is up to date is key. Microsoft issue updates regularly, as standard, to fix any known security bugs. If your software has reached its end of life, then Microsoft will stop issuing security updates, so you then need to update to a new Operating System. In this instance, Microsoft have issued an update specifically for Windows XP, even though their support for XP ended some time ago. But if you are still using Windows XP, Vispa, or Windows 7 or 8, you should consider updating to Windows 10.
The same applies to any other devices you might have, such as tablets and phones, apply any manufacter updates as soon as possible.
Antivirus Software
Ensure that you have a virus checker installed on your computer and set it to update and scan automatically. If you're not sure if that's happening, check your antivirus software now. Antivirus software will protect you from infected email attachments, and compromised websites. Make sure it's got it's latest virus definitions installed, and do a scan on your system. If you don't have an antivirus program on your PC, then download and install one as soon as possible. There are free programs available, or free trials, so start there if you're not sure which software you want to use at this point.
Use Good Secure Passwords