I will list down steps to secure your macOS & iOS Wi-Fi Network.
Step 01: First things first, Update you Macintosh, iPhone, iPad, iPod touch & even AirPort Express, Airport Extreme base stations for latest software using Mac App Store.
Step 02: Choose Unique & Safe SSID (Service Set Identifier) Wi-Fi network name
Wi-Fi network name is case sensitive. Choose a unique name for your network and that isn’t shared by other nearby networks. If your SSID isn’t unique, Wi-Fi devices will have trouble identifying your network. This could cause network device to fail to automatically connect to your network, or to connect to other networks sharing the same SSID.