Thank you for your feedback and advice!
Wow, it is great to meet a person here who knows about our main desktop software IP Video System Design Tool. To import a floor plan in the lens calculator the user can click on a small house button in the bottom of the screen. Yes the button is not in the toolbar.
This video shows how to import a background image 1:40 https://m.youtube.com/watch?v=NE7eTx1aPpg