You don’t need special software. PowerPoint 2013/2016 has a built in feature allowing you to record a presentation with narration. You can then save the file as a video for uploading.
In PowerPoint, prepare and save the presentation you wish to use.
On the Slides Show Tab, select the Record Slide Show Button. Work through your presentation, adding narration as necessary.
Select File, Export, Create a Video. Your file will be saved in a Mp4 video format.