I haven't done any work on automatic transmissions.
(Note: a quick google search for "honda accord v6 2002 automatic transmission problems" shows many issues with that transmission.)

General repair questions on your problem.
What did you replace?
(automatic transmission, torque converter, both?)
Where did you get the parts?
(any guarantee on the parts)
Did you torque the bolts to the correct factory spec?
(hopefully, using a click type torque wrench and info from the honda factory manual)

things it could be:
-automatic transmission not in Park or Neutral setting
-bad torque converter (stuck in "lockup mode")
-bad replacement transmission

if all else fails, call a mobile local mechanic.

take care,
ChrisS