OTM and Symposium are two different things. Symposium as you know is your call center server and controls routing calls to agents based on skillsets, scripts and what not. OTM is a graphical interface to the PBX for set administration, such as adding, removing, changing phones, names, button programming, etc.
I don't do much with OTM, since I learned set admin the old fashioned way through the TTY. There are some pretty slick things you can do with importing spreadsheets and what not to build new systems, but I'm not the guy to explain how all that works.
You might have more luck in the Nortel Meridian forum. This old Bay Networks/Optivity forum is pretty much dead.