Login to GeekSeller, go to Account > Profile Information and API, you can insert here your JET API keys.
Remember to refresh token after updating your API Keys:
Keys can be found on your Partner.Jet.com. Be careful with coping them to make sure you are using proper keys. There are two types of keys: TEST and LIVE:
Just after your Test API step is done and you did not upload to JET products for review yet, this screen will show you live credentials:
To get TEST credentials while you are live already:
To get LIVE credentials while you are live already: