Select Library from the navigation menu on the left.

Drag and Drop the Video from your computer that you want to upload or

press Click Here to browse your computer files for the image to add and click Open.

The Item will begin loading and show a progress bar. Once it has loaded, it will show "processing" in your library.  

Feel free to navigate throughout MeshMail while the video is processing. You can come back to the library at any time to check the progess.