How do i make the nec electra professional phone not ring

You will probably need to add the extension name via system programming. The following installation manual for the NEC Professional Level ll phone system may help (copy & paste)
http://pdf.textfiles.com/manuals/TELECOM-A-E/Electra%20Professional%20Level%20III%20Install%20Manual.pdf

Ringing is assigned in system programming, usually done by the service company unless you have a phone tech or IT guy/gal who handles this.

return it where you purchased it.

ringer don't ring incoming calls

hit feature key, then dial 9 # from the operators phone

this has to be changed in system programming

only if your key system has caller id cards installed.

If your main system cabinet (in some closet somewhere) is plastic, you have the NEC Electra Professional Level I system and the DND cancel procedure is <FNC>, 60, <FNC> when the phone is idle. If your main system cabinet is metal, you have the NEC Electra Professional Level II system and the DND cancel procedure is <FNC>, 69, <FNC> when the phone is idle. You can also press "42" while hearing intercom dial tone. The most common cause of accidentally setting DND is by dialing "40" while hearing intercom dial tone (Level II system).There is a slim chance your main system is not the Electra Professional series. If either of the above do not work, let me know.

The NEC Electra Professional Level 1 has a maximum CO line capacity of 8 in any configuration. If you need more outside phone lines, you will need a different system. If you need to limit cost as much as possible, the cheapest avenue would be to upgrade to a used Electra Professional Level II. That way you can still use the same telephone instruments, but ALL cabinet hardware would be different. Also, you can only get to 8 outside lines if you have software level 3.00 or higher by using the COI-C(2A)-10 card. To verify which software version you have, I think you press FNC(3) on sta. 10 ( or the first station in the system). If that doesn't work, let me know, and we can access the system program to verify version number.

Not sure if I understand your question correctly, but I think I just learned how to do that on an electra professional. Memory block 4-1-1 lets you go through each of the internal extensions, and you can set each extension to ring when a call comes in from any/some/all of the outside lines.
to reach memory block 4-1-1, I used a multi line terminal connected to ports 1. Press fnc => hold => # => 0 => * => line key 4. Use the fcn(?) key to cycle through the internal ports, the line key buttons to map each of the 4 lines (presumably line keys 1 through 4 on your system).
As to where to get a manual, I am not sure, I have 3 thick binders... good luck