There is no real secret to the MKR2UNO.
The real secret is remembering that the MKR series are 3.3 volt boards but many UNO type shields require 5 volts.
Then there is the fact that the UNO is a different MCU to the UNO so not all examples for the UNO will work on the MKR.
In theory you should be able to just wire out to a shield but remember to also keep the wires as short as possible and take into account the two points mentioned.
There are multiple motor shields for the UNO so you will have to look up the specifications of the components used on yours and ensure they are cable of running with the 3.3 / 5 Volt logic.
Also consider that 9 volt batteries tend to have a very very short lifespan especially when used with motors.