You can configure an existing project by selecting it in the Project Explorer and then either right-clicking and choosing Properties from the context menu or pressing the shortcut key of Alt–Enter. The Properties dialog lists the property categories on the left (in a tree) and the fields for setting the properties of the selected category on the right.
Note that most properties can be configured during project creation, because the New Project wizard shows many of the same tabs. The exact tabs and fields shown during creation and when the properties are accessed at a later time depend on the project type.