How can a submission upload more than 1024Kb of a video or photo?

also, how can a submission upload a .MP4 video

If you wish to change the max upload size, you can follow this guide: https://www.jotform.com/help/33-Changing-the-File-Upload-Size-Limit.

If you wish to set the allowed file types, you can follow this guide: https://www.jotform.com/help/29-How-to-Change-the-Allowed-File-Types-in-the-Upload-Field 

I hope that helps.