DTM was removed somewhere in the release cycle of V5 software, actually at the time it was moved to the Manager. Now it is gone. A stupid decision, too much input from suits and not enough from users.
On V8 you have to use "Performance Management", it will draw all kinds of graphs. PM uses COL - Collecting Agent. So you have to activate that too (Base Admin, Application Control). COL collects call logging records, which are then passed to PM to create graphs and stats.
It will take you about five million years to configure it. DTM was a nice app, simple, fast and useful. PM, not so much.