The video file needs to be 500MB and below.
Below is a guide for both android phone and iPhones. The images shown is for illustration. It might differ depending on the model of phones you are using.
Android
Open your camera and go to settings.
Go to video resolutions.
Make the necessary changes to reduce the size of your video.
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For iPhones
Open your camera and go to format.
Choose most compatible.
Make the necessary changes to reduce the size of your video.