Those CLI guys sure like to play with their zypper!lol!
Okay, since you are coming from the Windows world, you likely are not that familiar with the CLI (Command Line Interface), although you might be.
zypper is the application used for managing updates, installs, uninstalls, and so forth in openSUSE.
However, there are GUI frontends that will take care of this, so you do not need to plunge into the CLI right off the bat. You may, if you wish, or you can start moving there, in time, when you are more comfortable with Linux. Eventually, you will find the CLI is far superior to GUI for certain tasks and you will begin to prefer it in some cases.
In the meantime, I suggest you use the power of YaST.
NOTIFICATION OF UPDATES:
An application named Apper is installed by default. You will notice it checks for updates and pops up a notification balloon to inform you when there are any. It sits in your tray when there are updates, and you can click on it and click on the Install button that shows up there.
**INSTALLATION OF UPDATES:
**
However, I suggest you do somewhat as I do. When the notifications pop up, instead of running from Apper, as I just mentioned, follow John’s second suggestion:
Choose YaST from your menu, then click on Online Update. By default, this will automatically check that the software list is up to date, check for updates, then present you with a list of system updates. All you need to do is click on the Accept button and wait for it to do its thing.
After that, I like to run the remaining additional software updates that Apper shows.
INSTALLING/UNINSTALLING SOFTWARE:****
To install ClamAV, again choose YaST from your menu (unless you still have it open from the above exercise, then just switch to it), then click on Software Management. It will also, by default, automatically check that the software list is up to date. Your cursor will be blinking in a white text entry box with a Search button beside it. Just type clamav in there and hit the Search button. The rest is quite intuitive.
You can use this latter method for installing and uninstalling what seems like an almost-endless list of software.
As John points out, though, it is unlikely you need to bother with ClamAV, but perhaps if you are dual-booting Windows or plan to share any of your Linux files with Windows machines, you might then want it.
I do not bother with it, so far, as my Windows environments include good scanning software that will catch things before they can act.