Uploading jpg and png photos

I've tried to upload a photo into "My Photos" on this site.
Same photo but one copy I did some work in Windows "Paint".
The original photo uploaded no problem, but the copy that I used in "Paint", I'm getting a message "exceeds file size limit".
What am I doing wrong?
I did notice that the one photo is called jpg (original) and the "Paint" one is called png.
Would this be a problem?

Just upload to any other photo site and html the image link into the listing. Easy peasy...

Yes, I could do that, but I'm going to do a "How to" post and want the photos be seen for a long time.

I'd expect that if the png file type were the problem, the error message would be more specific, i.e., "wrong or unsupported file type."

Do be aware that the file size of a jpg and png of exactly the same image will be different due to the file compression issues. This will also differ because you "did some work" on the file, and to the extent you made that worked file more complex, the compression will necessarily produce a larger file.

So either convert the png file to a jpg, or increase the compression, or both.

Thanks, found a program to convert.