An anti virus app AND an anti-malware app running together should keep you clear (free, or paid do the same things.) Each also allows you to do a "scan" for virii/malware at any time. Just open the application and click the "scan" button. (If you have multiple hard drives, it might ask which to do, or if you want all done) It will check all of the files on the selected drive(s) and list and usually isolate, (often called quarantine) the files it thinks are bad. Then you can look at them to make sure they are actual virii/malware and delete them.
NOTE: After you find some and remove them, do a restart of the computer and do the scan again just to make sure you got them all. There are some that will hide parts until you remove other parts. Then the hidden ones become visible. If you don't, they can reinfect your computer all over again. Repeat the process until you get a 100% clear scan.
Download and run these FREE programs in the order I list them: CCleaner, Glary Utilities, SpyBot and Malwarebytes. I've been using them (and their FREE updates) for years now. Never had a problem.
Install antivirus software and check for viruses
In addition to AV, run a scan with the free version of Malwarebytes.