Every time you finish the work on the video and close the app, you are asked whether to save a project or not.
The project file stores all the changes made with videos, it also allows you to continue working on a video or export it as a video file.
Please note that you do not need to re-add the video exported in the trial version, but a MEPX project file.
This is the file that contains your work.
Please see the menu File - Recent Project. Choose the one at the very bottom of the list as the earliest created.
Else, please look up the earliest created MEPX file on your hard drive.
If a watermarked file is added to a project, it will not export without it.
Please note that it is impossible to get rid of the watermark from the existing video, but if you have a *.MEPX (or *.MEPB, *.MEPS, or *.MEP)project file, you can re-save it after activating the program and then your video will be saved without a watermark.