You don't need to deploy them; they start working as soon as they're built. Think of every ship you build as being built in orbit around your planet.

As a starter it is often hard to gather enough energy so Solar Satellites are a viable option. It also is a requirement for techs. But be aware that asap you will find yourself needing energy compensations that will require +500 sats for your planet it is time to abandon investing on satellites and focus on fusion energy. That is the way to go from there otherwise you will always be farmed for crystals by other players who will destroy those extra satellites.

And agreed to what sloth said.