You will need to define the material "Rockwool" in Material properties and then assign it to the appropriate geometry of insulation.
To check how to define a material in the "Engineering Data" tab (as shown in the figure below), you can take a look at the following Ansys Help Link: 6.4. Material Properties (ansys.com)
How to access Ansys help links
Guidelines for Posting on Ansys Learning Forum
Please Login to Report Topic
Please Login to Share Feed