I have replaced my motor on my outdoor unit but can't remember how the wiring goes back to dual capacitor, I have three wires, brown with red mark, red and white. Which goes to common and fan and which terminal does the other wire go to?

Well the first thing is that you should have bought a new capacitor, one that the motor that you bought requires. You do not have to buy a dual capacitor. Depending on the HP of the motor the capacitor may be something like a 7.5 uf 370 volts.

Now about the wiring, you only have three wires so if you connect to the old capacitor that you already have, the brown will go to the post on the capacitor marked fan, the white will go to the center post, or the one marked com, this post should have at least one yellow wire on it already that is coming from the contactor. The third wire will go to the contactor, on the pole that the yellow wire is not connected to.

If you do buy a new capacitor this is how the wiring will go, after removing all of the wires going to the old motor you will then connect the brown wire to one side of the new capacitor. The white wire will go to the same side of the new capacitor. The black wire will go to the side of the contactor marked T-1 or lets say the top terminals on the contactor.
You then will have to install a wire from the side of the contactor marked T-2 or lets say the bottom side of the contactor, this wire will then connect to the side of the new capacitor opposite where the brown wire is connected.

Black to T-1 on contactor
Brown to one side of capacitor
White to other side of capacitor
Jumper from same post white wire is on to T-2 on the contactor.