I was as confused as you are.
I followed these steps posted by PANDO (thanks Pando) on another thread and it helped me out. Basically, the normal installation of 8i doesn't include the "Management Structure" part. You need to use your 8i CD and load that part up.

Do this:

[by Pando]
To install OMS get your 8i CD and install management structure part, after this instllation you will see a new service called Oracle Management Server in your services, just start it and then you can connect to that server from your console in other machine or the same machine where OMS resides.

Hope that helps!
- Magnus