Wi-Fi outside of home

You need to use Public Wi-Fi, see this Apple article: Use captive Wi-Fi networks on your iPhone, iPad or iPod touch -> Use captive Wi-Fi networks on your iPhone or iPad – Apple Support (UK)

Nowadays, Public Wi-Fi is offered for free, in big cities, shopping centers, in Public Transport (bus & train), airport, restaurants and others.

That depends on where you live.

If at the moment you are away from home and there is no Public Wi-Fi, you have to use Mobile Data, for sure go to -> Settings -> Mobile network -> Mobile Data -> ON.