First, decide whether you would like to do a traditional speech (showing your face) or if you would like to avoid showing your face on camera. Then, decide whether you want to spend some time editing your video. Check out some different options below.
Free apps for editing videos
Android: https://play.google.com/store/apps/details?id=com.adobe.premiereclip
iPhone: https://www.apple.com/clips/
How to record a screen-capture video using PowerPoint:
Watch tutorial: https://www.youtube.com/watch?v=kQwGEY4IDi0
How to add extra-cool animations:
Watch tutorial: https://youtu.be/OU5vyHaCCXg