How to change/add a logo in a navigation bar
To change a logo or add a logo in a navigation bar, first make sure you have a navigation bar located on the canvas (you can use either a "Navigation bar" block or a "Navigation bar" element).
Once you have a navigation bar on your canvas, proceed to click on the logo to bring up the right side bar:
In the right sidebar, click the tab labelled "Functionality":
At this point, you can use the image selector to open up the image library modal. It's important to keep in mind that the application does not automatically changes the dimensions of the image to choose to use as the new logo. It will, however, display the choses image using a maximum width (this to ensure the chosen logo image does not appear to large in your navigation bar).
After choosing your new logo image, click the button labeled "Update" to save your changes.