To add a time history load case

To add a load case for your time history load, use the following procedure.

Time history can not be used with a load group. Only load cases have the option for the time history category.

On the Model ribbon tab, select the Load Case tool in the Loads group.

The Add Load Case dialog opens.
Type a unique Name for the load case. This is helpful in identifying the load case.
(Optional) Type a Description for the load case.
Select Time History from the Category drop-down list.
Click OK. The load case is created and selected as the current load case.

You may now add either time history ground motion or time history nodal loads to the this load case.

Time history load case details can be viewed and edited by selecting the Time History Load cases tool in the Reference group on the Spreadsheet ribbon tab.