For Phones, tablets, etc: Record the moment you want to submit with any iOS / Android recording apps. For PC: 1. Use Memu (better than Bluestacks, has built-in screen recorder – no Bandicam needed). 2. Bluestacks + Bandicam
If the size of the video file is less than 20mb – Just attach the file to your e-mail message. If the size of the video file is larger than 20mb – Use Google Drive or Upload the video on Youtube and share the link.