M. To add a time history load

To add a time history load to the current primary load case, use the following procedure.

Select the current load case in the program status bar.

Either:

On the Loading ribbon tab, select the Load Items tool in the Loading Specifications group
Tip: This will add the load item to the currently selected load group selected in the program status bar.

or
In the Load & Definition dialog, select a primary load case in the Load Cases Details list and then click Add.

The Add New Load Items dialog opens.
Select the Time History tab.
Select the Load Type:

Time Load for a forcing function that applies forces or moments to joints

or
Ground Motion is applied global to all supports as an acceleration type
Select Direction in which the load is applied. Time Load types are applied in FX, FY, or FZ for forces and MX, MY, or MZ for moments. Ground motion types are applies in one of the three global directions.
Select the arrival time for this load from the arrival times in the time history definition parameters.
Select the load definition type from the Defined Types drop-down list. The list includes the definition number and function type.
(Optional) Select the results type from the Response Types drop-down list.
(Optional) Type a Force Amplitude Factor to multiply for the forces, moments, or accelerations at the joints.
Click Add.

You must assign the time history load to the joints to which it applies.