To apply a temperature load to a surface

To assign a load due to a uniform or differential temperature to a surface, use the following procedure.

Select the surfaces that will all have the same temperature load applied.
On the Surface ribbon tab, select the Temperature tool in the Loads group.

The Add Temperature Load dialog opens.
Select the Load group or case to which the load will be added from the drop-down list.
For Axial Expansion loads, type the Temperature change experienced by the entire cross section.
For Differential Loads, type the temperature differentials experienced across the local Z directions of the members.
Click OK. The dialog closes and the load is applied to the selected surfaces.

You can edit temperature load values for the current load group or load case by selecting the Surface temperature load tool in the Surfaces group on the Spreadsheet ribbon tab.