what about reading the documentation? App Inventor Extensions: WiFi | Pura Vida Apps
Note : Android will get more and more restricted. The ConnectSSID method does not work anymore starting from Android 10. According to this Stackoverflow answer: For API30 we can use a new Intent action, for API 28 and below we can still use the old way of adding Networks, but for API29 we have some kind of gray area where I was not able to find a good solution yet. . Which means I will wait until App Inventor targets API30 until I hopefully will be able to provide a solution for the ConnectSSID method again…
Taifun