Fields are not added directly to a project, but rather to a table in the project. Select a table from the Project Browser and then click the 'New Field' tool bar icon or open the Tables menu > Fields > New Field.

Select the field by clicking on it in the Project Browser (if it is not already highlighted) and click on its name or press F2. A cursor will appear allowing you to rename the field.

Select the field by clicking on it in the Project Browser and press the Delete button.

In AppGini, click with the mouse on any property and press F1 to obtain help about its function.