Access keyとSecret keyの取得方法 (how to get Access key and Secret key)

I would like to use LINE Ads API to get a reports (ex. impressions, clicks,,,) on the ads I submitted.

Please help me on how to get the Access key and Secret key.

The document tell that:

1. Activating a Group for accessing to this API We send an invitation email to your email address which is applied. It invites you to a Group which is associated with information for accessing to this API.

Document link: https://developers.line.biz/en/docs/line-ads-api/overview/#authentication

But I don't know how to "Activating a Group for accessing to this API", I also searched about it but no result. Could someone help me or tell me "LINE Ads API" feature still activing or not?

Thank you for your help.