We can add additional information to our model to display on Isogen called an Isogen supplemental. 

On the CADWorx Plant I ribbon on the Isogen section of the ribbon we have Isogen Supplemental.

Here we can apply instrumentation, penetrations (floor/wall), Flow Arrows, and Tie In's.

The only thing to keep in mind is a Supplemental will not route in the Z axis.  The following example will be how to place a 2-level instrument.

First I will place a North UCS at the location I will placing my Instrument.

Then I will route the Instrument up from the THRD valve assembly and put in my values.

The follow isometric is the output from Isogen and my current style settings.