You can change the selected environment and its mode via the Select Perspective dialog. Just keep in mind, that the project will not be converted automatically. When you select another perspective, only the GUI will change but the project will not be migrated to the new framework.
To open Select Perspective dialog
However, if you need to change the project's framework, you must convert it to the required framework.
To convert an enterprise model to another Enterprise Architecture Framework (EAF)