What app do I need to install before using the DJI Mini 5 Pro?

The DJI Mini 5 Pro can only be used with the DJI Fly app. The latest version can be downloaded from the DJI Mini 5 Pro Downloads page on the official DJI website. If you are using the DJI RC 2 as the remote controller, it already comes with the DJI Fly app pre-installed.