Okta's management APIs live on your org's domain at https://<org>.okta.com/api/v1. API tokens use Okta's own SSWS scheme.
Create an API token under Security → API → Tokens in your Okta admin console and send it as Authorization: SSWS <token>. In the examples it's written {{OKTA_API_TOKEN}}; {{OKTA_DOMAIN}} is like example.okta.com.
Full reference: https://developer.okta.com/docs/api/
curl "https://{{OKTA_DOMAIN}}/api/v1/users?limit=10" \
-H "Authorization: SSWS {{OKTA_API_TOKEN}}" \
-H "Accept: application/json"
curl https://{{OKTA_DOMAIN}}/api/v1/groups \
-H "Authorization: SSWS {{OKTA_API_TOKEN}}" \
-H "Accept: application/json"
curl https://{{OKTA_DOMAIN}}/api/v1/apps \
-H "Authorization: SSWS {{OKTA_API_TOKEN}}" \
-H "Accept: application/json"