When we set up the frequency response analysis, we must specify the node numbers to which the force will be applied, assuming that we will not be applying the load only as ground motion. We must use the Results environment to find this information.
- Click the
Results tab above the browser (tree view) to enter the Results environment. - Deactivate the
Results Contours 
Displacement Show Displaced Show Displaced command to show only the undisplaced model. - The node numbers will be easier to read if the display of all mesh and feature lines is disabled and the results contour colors are removed. To do so...
- Select
View Appearance Visual Style Shaded. - Select
Results Contours Other Results None.
- Select
- Activate the
Results Options View Show Numbers Node Numbers option. Your model should look similar to the one shown in the following image. 
- Write down the node numbers of the four top nodes of the model, as shown on your display.