How to add OAuth provider correctly

How to add OAuth provider correctly

Hi, I have an internal rest api that accepts oauth, and when I attempted to request add oauth provider for an alarm action, there are some config items that I cannot be sure: 

the rest api accepts token request in this requirement, illustrated in curl is: 
  1. curl --location --request POST 'http://[hostname]/[api_name]/Token' \
  2. --header 'Content-Type: application/x-www-form-urlencoded' \
  3. --data-urlencode 'grant_type=password' \
  4. --data-urlencode 'username=[username]' \
  5. --data-urlencode 'password=[password]'

In the add oauth provider form: 


Can I confirm the following:
1. is grant type == client credential correct? 
2. should I provide the client id as username and secret as password in the 2 boxes, or add in the request body as shown? 
3. should use Basic authentication with the default method as shown? 

PS: I tried some but did not get luck, hopefully you can provide some guides.
Thanks