To add a time history ground motion

To add a ground motion load to the structure supports, use the following procedure.

You must have created a time history load definition using acceleration data and a time history load case.

Ground motion is automatically applied at all of the supports of the structure.

On the View ribbon tab, set the active Load to a time history load case in the Active Load group.
On the Model ribbon tab, select the Time History Ground Motion tool in the Loads group.

The Add Time History Ground Motion dialog opens.
Select a time history load cases from the Load drop-down list.
Select an acceleration time history definition from the Definition drop-down list.
Type a Start time with respect to the time history definition the ground motion begins.
Type an acceleration amplification. Factor to use for the load.
Select the global Direction in which the load is applied.
Click OK.

You can edit time history nodal loads for the current load case by selecting the Time History Nodal Forces tool in the Node group on the Spreadsheet ribbon tab.