Logos help your listener to identify your station. It also helps potential listeners decide to download your app from the app store. It's important to have a great looking logo image, because until your listener downloads and launches the app this is the first thing they will see.
If your station doesn't have a logo image yet, there are lots of great online resources that will let you create your own, or services you can hire to create one for you.
Still not sure what a logo image is? Think of the Nike swoosh, or the Amazon.com smile. They are visual representations of the brand.
Size and Resolution: Make sure that your logo image is 300x300 or 600x600 pixels with a resolution of 72ppi so that your logo looks it's best on the app.