ClamAV, this is a command-line utility. If you want a very configurable graphical version, download
ClamTK from the software store included in PureOS instead. You can set it to run automatically on a schedule, or use it on demand to scan a file or an entire directory. It can also scan incoming email. In general, you only need to scan your Home directory. The scan might occasionally find a “potentially unwanted application” (PUA), such as a spreadsheet macro, but I wouldn’t worry about that. You can decide to ignore it or not.
ClamTK/ClamAV automatically checks for new virus signatures, so it’s pretty much on auto-pilot after you adjust the settings to your liking. You may see a message (in the UI) that there is an “update available,” but this is for the graphical interface, not the virus signatures.
Because Linux doesn’t automatically grant admin privileges to the user/owner, and requires that to do anything that affects the operating system, it would be difficult for malware to infect the machine, so long as you’re careful: if you download anything from the internet, make sure you verify the checksum/signature. Don’t install things you’re not sure about. Using
ClamTK/ClamAV is an extra step for added confidence, and to make sure you don’t pass on a Windows virus to other people.