To replace the logo image that displays on the top bar of your app, navigate to Edit > Automatic Layout Editor and click Logotype.
Then click Choose Image to select one.
Click the [+] button to choose a file on your computer. Try to avoid files bigger than 300px on it’s width. For a better looking app, choose a transparent file such as a PNG or GIF file. After your done, click the Close button and then Save on the top bar to commit your changes.