No offense to the respondors, but you have to learn how to do these things somewhere. Warning the OP that it is not a activity performed lightly and should be done during non-business hours and at low usage periods is a good idea, but telling people not to do it at all..
Isn't the point of these forums to learn and ask questions?
Kodaker, as TAnselm said, it's in the "upgrades and conversions NTP" which you can find
here. (I know this link isn't working properly, but I left it that way anyway.) I would try to link to the exact document, but since you didn't specify software version and exact hardware, it's hard to give you an exact link.
If you haven't done this before I'd offer two recommendations (1) consider getting a tech from a vendor to supervise the process until you're confident you can repeat the procedure without needing documentation, (2) only perform a parallel reload during non-business hours or during scheduled changed controls (or both).
Your entire phone system will be down during a parallel reload.
Also, there is no reason to perform a parallel reload as part of any "routine" maintenance plan. The only reason I ever perform a parallel reload is because I'm upgrading a system or the rare case of resolving corruption. If you're doing an upgrade or dealing with corruption, you really should have your maintenance vendor involved.