You are using the variable pfr twice, so the first assignment gets lost. If you change your code to use different variable names like so:
pfr_motor = pifacerelayplus.PiFaceRelayPlus(pifacerelayplus.MOTOR_DC)
pfr_relay = pifacerelayplus.PiFaceRelayPlus(pifacerelayplus.RELAY)
should work. Similarly, if you want to do something with the relay, use the pfr_relay variable.
By the way, these are very basic programming constructs (variables and object references) so make sure you get comfortable with programming in general and programming in Python in specific before attempting more complicated code.
UPDATE: I've done a quick check in the PiFaceRelayPlus docs, and found the following example code (executed in the Python Shell):
>>> pfrp = pifacerelayplus.PiFaceRelayPlus(pifacerelayplus.MOTOR)
According to this example, you should only have 1 reference to your PiFaceRelayPlus (the
pfrp = ... line). The first argument of PiFaceRelayPlus is the add-on board you used (in your case the Motor DC board). Once initialized through this assignment, you can now use the
motor lists to access motors and relays at the same time.