my pc is recently affected by virus.so i want to reinstall windows 8.when i click on recovery option refresh your pc without affecting your files,this windows appear as shown in image
.below that option another option exit.reinstall windows to its factory setting.this option also showing the same.what to do next.i installed the windows 8 from bootable pendrive.
That's basically telling you that you need to connect your Windows 8 installation media so that it can use it to do the refresh with. It needs to be connected to be able to do a refresh or reset of Windows 8. That's all.
Since you were dealing with a virus, I would recommend to boot from your Windows 8 USB, and do a full clean install instead to start fresh to help make sure the system is clean afterwards.