Google is our best mate. If you've got a simple image, you can run it through some free websites that pop up in Google to remove the background for you.
We've even pre-populated a search query for you below:
https://www.google.com/search?q=image+background+remover
While we're on this, it's worth knowing the following:
PNG VS JPG
PNG = can have transparent backgrounds
JPG = can't have transparent backgrounds
Basically, you'll end up with a .PNG file with a transparent background that you can upload. Nice.