Hello ljos,
The IoCore has 8 General Purpose Inputs. These GPI pins can be measured and used in show control.
To start you will need to know how you motion sensor works.
I know of some PIR sensors which open and close a relay, for powering lights. However some other give a voltage, to inform some other device it has seen something.
The relay one is relatively easy to connect. Just connect the first wire to the output of the relay and the first pin of the GPI. And connect the second wire to the input of the relay and the second pin of the GPI. The first and second pin are both part of GPI 1. Now you have to go to the settings page of the IoCore and set GPI 1 to Digital.
You may want to take a look datasheet of the IoCore for more information about wiring.
Best regards,
Guido