There is no bus to DTD at the TTC. You can either, depending on where you are in Epcot, get a bus to SSR and then walk over to DTD (or take their bus), or walk to BC and take their bus to DTD.
If you are towards the front of Epcot, the bus to SSR might be faster. But if you're in WS, then exit the International Gateway and walk over to BC.