Wherever you are in your timeline (denoted by the red line on your timeline) you can add an action there. So in the screenshot below you can click on the actions button (circled in red) and add your action code inside of the actions window. Inside of your action window it will appear as "Trigger @ 0ms", where 0 in this case is the beginning of the timeline. Hope that helps!
I added a shortcut for that in preference.
Otherwise you need to go to
1.Position to be play head on the timeline where you want to be insert the new media.
2.Select Edit > Split Selected at Playhead or press Command-T.
3.Drag the new media onto an open track on the timeline and align the start of the media with the playhead.
4.Drag an end of the new media to adjust the media to only the portion you want to insert.
5.Drag the new media into blank space between the two clips.
6. This crops the original clip. Drag the new media into the blank space between the two clips.
Ah, this is exactly what I was looking for. I guess I overlooked it when scanning the menus. Thanks for your assistance!
My pleasure. Thanks! Good luck on your project.