We are new to 128I and are trying to get SLT Phones to ring. Do we need a ring generator? Where does it connect?

First, do you have an analog station card in there? If so, what ports are they? Do you know where they break out to on the 66 block? You need to know this before you can even get into programming

If you are refering to the 28i you do not need a ring generator. A ring generator is only used on the 384i and 704i. 384i and 704i is a cabinet the size of small electrical transformer. The 28i is the size of a electrical meter.