Stop sharing printer over WiFi
The User Manual has no documentation on any security features for that printer.  So, regardless if it's WiFi or connected to Ethernet, it's a wide open printer on the network.  Business class printers will have the ability to lock out users through a variety of methods - I always recommend these printers over the consumer ones for this (and many other reasons)
The &quot;Printer Sharing&quot; section on your Mac, is for printers connected to your Mac. It allows you to manage who/what can print to that printer via your Mac.  Technically, you can share a networked printer, but as stated before, since that printer is &quot;wide open,&quot; anyone can get to it regardless of the policies you configure on your Mac.
So, you have two options:

create your own small Wireless network that only you have access to and put your printer on that.
purchase a USB cable and connect your printer directly to your Mac.

(Option 2 is probably the most effective method).