Sense should only be installed by a licensed electrician. Installation itself is quick and easy, but it requires opening up your electrical panel and connecting current sensors to the service mains. These wires are live, even with your main breaker switched off, and are thus very dangerous. Only a licensed electrician is qualified to work in these conditions.
When speaking with your electrician, let them know that Sense is an energy monitor that installs in your electrical panel with two clamp-on current sensors around the mains, and a 240V breaker which Sense uses for its power supply and also to measure voltage on both legs. Unless you have a spare 240V breaker in your panel, your electrician will likely need to provide a new one.
You may also wish to share with your electrician this blog post and video to help them get a better idea for what's required.
A set of installation instructions is also included in the package, and available online.