1) To authorize a client application with the secret post type, you need to add the client_id and client_secret parameters to the existing request.
Example:
client_id = id-wEkziJ6jW6dJg36GT2a1ww7C4BpLeXCrMRLAVgOyQNgSKZV
client_secret = N2f9TvacRuBsRLQ2mSw9HOQ2GoLCDIaDPsoXfT0xNu8kcuAZSO
Example request in cURL: