Hello,
If I were you, I would consider using the general purpose bits, and then connect that bit to a digital output in the PLC or in the UR program. Instead of writing directly to an output in the UR from the PLC.
Go to Installation - IO Setup and scroll down on the Input list until you find GPbi[0] (General Purpose bit in 0). Rename this signal to something of your own choice.
Now, if you have imported the UR Data Type as described in the PROFINET instructions, you should be able to locate bit[0] as Register[0] located on Q24.0 in your case.
If you set register bit Q24.0 to True in the PLC, your GPb[0] will become True/1 in the UR. 
Then you can use it for whatever you want. The GP input will become visible in the Input dropdown menu, when you rename it:
Then you can use the input for controlling a DO in the UR in a thread:
You can also write directly to the digital output in the UR, but you need to use the Mask bit, as well. And the UR will not have control of the output anymore.