Add place by marking the ellipse tool on toolbar and clicking at the canvas to spot, where you want to put the place.
Perform double click to open the properties window of the place.
You can edit these properties only at specific types of Petri nets. Properties ID, Name, Marking and Color are available for every type of nets. Property Type is only for EvPN and it sets the type of place. P is the standard which is similar with GPN and TB nets places. The type Pe requires a predicate to work, and the Pf needs a function to be defined for chosen place. Property TB Tokens is enabled only for Time-Basic Nets. If you want to cancel the addition of places, just unmark it's icon on the toolbar.