in the router menu, there is a connected stations list - all the devices connected and their IP addresses/MAC addresses. usually in that part of the menu, there is a MAC Filter table, where you can ADD from the connected stations list devices into the filter table. you have a overall MAC Filter Enable/Disable and usually a setting that chooses between, FILTER OUT all those devices listed or Filter them in which translates to Disable the listed stations, or Only allow the listed stations. so you can list say your 5 devices, tick each one and say ADD to filter table, then ONLY ALLOW THESE DEVICES TO CONNECT, whereupon you must then tick the APPLY filter button, and APPLY to the ROUTER settings(requires restart of the router button). The way in which mac filter table is displayed and the buttons you need to press varies per router webpage. you must know how to get the router menu page up first, ie connect a device using a lan cable and LOGIN to the router webpage at the router address eg 192.168.0.1. you cannot display router settings via wifi connected devices.