I am trying to setup voice mail on a RCA ViSYS 2-Line Phone (25255RE2), and i cannot figure it out.

RCA ViSYS 2-Line Phone (25255RE2)

Here's the manual for your 2-line phone:
http://www.rca4business.com/products/pc/pdf/instruction-book/25255RE2.pdf

refer to pages 40-43 of your manual for "Answering System Operation."

To enable your Answering System, press and hold the "ans sys" button for 2 seconds.
The "ans sys" button indicator will flash.

To disable your Answering System, press and hold the same button for 2 seconds.
The "ans sys" button indicator will go off.