There is no 100% way to avoid virus other than staying of the Internet and keeping your PC turned off! However you can increase your chances of staying virus free by keeping your Antivirus/AntiMalware software & your system up to date on a daily basis. This keeps your system patched for the latest (known) vulnerabilities and your AV definitions up to date, and yes set it up to be done automatically because you can forget and one day missed can make a difference. Again, this doesn’t guarantee your PC won’t get infected but it will increase your chances of stating virus free.
Here are some free antivirus/antimalware software if you don’t already have any;
These are just a couple there are many more google it.
P.S. when installing any free software always read every screen to make sure you only install what you want and no extras sneak through. Nothing in life is ever 100% free, so be aware of what you’re installing, they might server up a small amount of ads or every so often give you a pop-up message but they are making money somehow, and if you can’t tell how they are making there money it’s usually because they don’t want you to know. Don’t be paranoid, just be aware. I use plenty of freeware I just read everything first so I know what I’m getting myself into. I don’t endorse any product I just use some more than others.
If you need any further help please visit www.xdnit.com and click on technical support, create a support ticket and we’ll get back to you ASAP.
It's my life, you're just along for the ride! 
Awesome thanks for the advice