On the same host where Web Jetadmin is installed:
Option 1: go to Start --> All Programs --> HP Web Jetadmin 10 --> HP Web Jetadmin.
Option 2: Open web browser of your choice and browse to http://localhost:8000
From another system running windows:
Browse to http://wja-server-hostname:8000 where "wja-server-hostname" is the host name of the server where HP Web Jetadmin is installed