You will need your login details and member number to download and access the Member Benefits App. This information would have been emailed to you when you joined the NZBA. If you cannot find it, please note that your login is your email address. Your member number can be found under Personal Details in your member portal.
Once you have those, you can download the app and start using it. Full instructions on how to do that can be downloaded here.
Or you can view a short video demonstration to assist you here.