The App can be downloaded from the respective reference Stores for Android and Apple. You can find it at the following link for Android and Apple, or by typing and searching for "StayPlus"

The credentials you use to log in are defined by you during the registration process. If you have forgotten them, there are the usual buttons to remind you.

No! Your credit does not expire and you can use it in the future as long as the StayPlus network is active.