Firstly, you need to create a layer version to be able to add fixture or another object into the floor plan. In this case, we will insert fixture in the "Fixtures" layer. We recommend setting the layer name to "1". It will be the first version of the floor plan.

To insert a layer version, right-mouse click on the layer and click on Add Version.

Add a layer version

Created layer version 

You can change the name of the layer in the sidebar of Quant Explorer in  Stores / Layers section. Here you can also create a new layer in case you need it. You can find out more in Floor Plan Layers manual.