The User Guide mentions creating table via drag & drop here: http://community.jaspersoft.com/documentation/tibco-jaspersoft-studio-us...
It should also explain that you can click on the palette item, then point & drag on the desired report band to define the table size immediately.
This is not very obvious at the moment and it's particularly important for tables, as the initial size determines the cells' size and even if you resize the table afterwards, it's not that straightforward to resize the cells later on inside the table.
I can confirm that this info is documented nowhere and should be added.
This is not obvious that the size can be set immediately with drag&drop.
Thanks for your feedback!