How to save PNG images to chromebook

Okay so I know this isn’t technically “Episode Based” but I really need help guys so please help a fellow Episodian out.
I have been writing a story (its published actually) called Talk’s Over-Rated but I didn’t really like my story line so I am wanting to do more with it.
This “doing more” idea that I have includes PNG images… Lots of them, but everytime I save a PNG image to make an overlay my chromebook only gives me the option to save it as a JPEG image and episode wont let me upload that type of image.
Now before anyone asks, YES, I KNOW THESE ARE REAL PNG IMAGES because I searched up the same ones that I save on my old laptop THAT WORKED and its still doing the same thing.
I really need help and I hope someone can get back to me soon, thanks!