If it’s your first import
By default, Motion places imported media files in your project at the location of the playhead (the current frame in the Timeline). You can change that setting to have imported media always placed at the start of your project (frame 1).
Set the start point of imported media
Choose Motion > Preferences (or press Command-Comma).
In the Project pane, set “Create Layers At” to one of the following:
Current frame: New media layers are added at the current playhead position.
Start of project: New media layers are added at the first frame of the project.