If it is a Siemens Comfort panel, you cannot plug in a separate monitor, but you can use smartservice/smartclient to remotely display and operate the TP.
As of TIA V14 the smartservice license is included in the panel.
Older panels also support smartservice, but then you will have to buy a license.
edit: To activate the smartservice on the panel, the option has to be activated in the source program and then compiled and downloaded to the panel.