Sorry I didn't understand the query clearly. Following is my input based on my understanding.
EntityName seems Mashup parameter of the selected mashup.
To add it we just need to go the Mashup which is selected in the name property of the Container widget.
In Workspace; click mashup and then click on Configure (Tool icon) to the Mashup Parameter.
Now the Container widget will show this as a widget property after selecting the Mashup name.
I hope it helps.