Is there anything a Receptionist / Switchboard operator needs to know to handle a EPABX?

Question

Where can I learn it?

Answer 1

The basics are pretty simple, in most cases most of the specifics you need to know are dependent on the company, how they work, and how they have the system installed.  Usually about an hour or two of training on the job is all it really takes, and most of that training will be specific to that company.