New to github contribution

I'm so sorry to write here since I don't have a real issue, but since this is my first time contributing (or intending to contribute) to a project I'm not really sure how things should be done. This afternoon I forked the repo and added the ability to change background color, background color of the border, style of the border, and foreground and background color of the title of the popup window. I would like to submit my changes to be reviewed (and hopefully accepted), but, as I stated, I don't know what/how to do it. Again, I apologize for all the confusion.