Let's take a look at the Properties panel, which can be found on the right side of your Vertabelo workspace.
If you want to change anything in any element within your diagram, you need to click the element and then proceed to the Element properties in the Properties panel. There you can do anything you wish with your entity, association, relationship, note or subject area – an element's properties are grouped in sections as expandable lists and there they can be edited.
Sometimes an element may have an error (missing identifier, looped relationship, etc.). You are able to see what's wrong with the element in the bottom of the Properties panel in the Problems section. The difference between this Problems section and the Problems section in the Model navigation panel is that here you see only those problems related to the currently selected element.