To create a Task through the Floor Plan, open up the Buildup and go into the Units Tile 

Select the Area and Unit you'd like to drop a Pin in.
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Once in the Unit, select the middle Icon (looks like a floor plan).

Select the Plan

To drop a Pin, select the icon on the bottom right corner 

And then select the area on the plan to drop the pin 

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You will then be able to create a Task 

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