RestAPI Authentication

Hello,

I'm trying to put data to PowerBI dataset from javascript.
But, POST https://api.powerbi.com/v1.0/myorg/groups returns 401 Unauthorized
How can I be authorized?

My step is
1. register myapp to azure AD, get clientID and clientSecret
    https://dev.powerbi.com/apps
    - Server-side Web app
    - Read and Write All Datasets

2. get access token
    https://login.microsoftonline.com/<tenant-id>/oauth2/token
    - resource=https://analysis.windows.net/powerbi/api

3. POST https://api.powerbi.com/v1.0/myorg/groups
    - Authorization: Bearer ey...mAtw

Any thoughts?

Thank you.