More information is needed in order to assist. Network-attached scanners are reasonably easy to configure, but you have mentioned that your multifunction device is attached to another PC. Is it a Linux machine, or running Windows. If the former, then it needs to be running a sane-server. If it’s a Window machine, then I’m not sure that you can scan remotely from a Linux client.
Let us know if you require further support with this. While attempting to post a reply, I managed to adjust your post unintentionally. Anyway, it looks like you know what you have to do.