I replaced my 2001 honda civic transmission and it still won't go in drive only reverse?

Now a flasing d light is on

Replaced with a used one? Then you might of got a bad one. As far as the light since it can't be driven and you have no way to get the code in the system. You'll probably have to have it towed to transmission shop for more help. Find one at ATRA.COM

It is a computer controlled trans. Pull the codes and start form there.