Hi Nick,

Once you created the event with the input parameter, go check your block instance on the page. You will see the event on the block.
Assign a new action to that event handler and the parameter of the event will be shown on the block properties (right below the handler).
Open the suggestions for that input argument and select the input parameter of the event.
Now your event handler will receive the value from the block, and you can assign that value to whatever you want.