I bought 2 SonOff to evaluate. One is the SonOff Touch US and other is the SonOff Basic.
The instruction guide it's not clear how to install in my scenario.
I have 220v in my house, and it's phase + phase. The actual bulb switch just has 2 wires.
How can I install them?
What is the voltage of the light bulb or appliance you want to switch?
If you are in the USA and the appliance is 240V then you have two hot wires to achieve 240V and should not use a single pole Sonoff as it only disconnects one hot leaving the other energized inside the appliance with a potential of 120V to neutral or ground.
If the appliance is 120V then you are working with one hot and neutral. Follow the diagrams that come with the Sonoff.
If you are in Europe you likely have a 230V hot and neutral. Follow the diagrams that come with the Sonoff.
This link will provide some information for you.