Welcome to the RingCentral Community

Did you purchase your phone(s) from RingCentral? If so they are already provisioned and are plug and play. Just plug them in and connect them to your internet source. If not, what brand and model did you purchase? Youll have to do a manual provisioning. Rather than taking the time to explain that procedure here and now, please advise whether you purchased RingCentral phones or not.

How do I set up our existing Yealink T27G to work with ring central?

Hello Frank,

Here are a few articles:

1) How to Install RingCentral for Desktop
2)  Connecting your RingCentral Desk Phone to Your Network

That's a little vague ;). As Jan stated, usually, the answer is just plug it in to a POE port use the power supply.  Do you want to share more details so we can help?