You can use Shotcut, free and open source software for video recording, to put together your video presentations. Shortcut provides guides and tutorials for this software, including:
Getting Started: Installation Guides for different operating systems
If you'd like to use more advanced features for your recording, the Shotcut Video Tutorials page also includes tutorials its advanced recording and editing features.
Open Broadcaster Software (OBS)
You can use the Open Broadcasting Software (OBS), free and open source software for video recording, to put together your video presentations. OBS provides guides and tutorials for this software, including:
Getting Started: Installation Guides for different operating systems
Quick Start Guide: Five steps to get started on creating your videos