Need help changing the header logo on a Soholaunch template

[silhouettestyle]

I am setting up my webpage, and I started in Soholaunch with a basic template. I'd like to take the default logo off and add my logo instead, but when I do this through template settings, I get an error stating that the image is too big. What size does it need to be?

Also, how do I access the html?

www.silhouettestyle.com