1. Create a free developer account at https://developer.justgiving.com/signup
2. This will generate for you an appId automatically
3. To apply for the Data API plan please submit a request for a plan change by logging into your JustGiving Developer Account > Dashboard > Applications > Edit > Review/Change Plan
or email us at firstname.lastname@example.org with details of your appId.
We will review that request to verify who you are and will act accordingly. We usually try to turn around applications in under 24 hours.