Assuming you have a recent version of Movie Studio I would do the following:
Place a copy of your mp4 file onto the Timeline in MS. By using a copy you ensure that the original is always available to you, in case of any "accidents"!
Make a cut (shortcut T) at the point where you wish the divide to be.
Delete one part (make sure it is highlighted and then hit your Del key).
Export the resulting new file (via File>Export Movie as ...[presumably MPEG-4]) under a new name.
Repeat the above procedure, ensuring you delete the "other half" of your file before exporting it, again under a new name.
@david-sahm Or you can place the cursor where you want split the clip into two parts & choose Split Movie, that will create two Movies that you can then export separately.