To add/change your logo, go to Site > Branding > Logo > click 'Upload'.
Click on the upload area or drop the logo image here.
Select the new logo and click 'Open'.
Now, a new logo has been uploaded to your website.
Once the logo is uploaded, refresh the front end of your site. Your logo will appear in the top left of the navigation bar.
Also, watch the video on 'Add Logo to Your Site'