Go to your wamp folder. Then scripts/
Edit onlineOffiline.php

$offlineText = "#   onlineoffline tag - don't remove
    Order Deny,Allow
    Deny from all
    Allow from 127.0.0.1";
    
...becomes...

$offlineText = "#   onlineoffline tag - don't remove
    Order Deny,Allow
    Deny from all
    Allow from 127.0.0.1
    Allow from 192";
    
Restart wamp.
If you want to know your local IP : Win+R, then "ipconfig"

This is the IP you should type on your other device (phone, for example) to access to your localhost.