
With basic knowledge of how a phone system works you should be able to install it yourself, it also comes with an installation guide. If you prefer not to, then a handy man that knows about phones should be able to install it. Keep in mind that to receive multiple calls your phone line must support this, some phone lines can accept 2 calls at the same times but most times the easiest thing is too have different phones lines working together, you can discuss this with your voice provider.
Alternativele you could consider switching to a VoIP (voice-over-IP) system where all the phones work using your internet, the configuration has to be done by a service provider but you do get the far more options to adapt the service to your business needs.