Authenticate with a Connected App
The first step in an API-based integration is to connect to Salesforce
and get an access token using OAuth. OAuth access token authentication is the most secure way to
authenticate SOAP and REST API calls.
If you are working in a Salesforce organization that has a Developer Edition, an Enterprise Edition, or above, verify that you have the API Enabled permission. This permission is enabled by default. This permission allows you to access any Salesforce API.
When you have this permission, you can connect to Salesforce and authenticate. Then make a request to REST or Connect API and check the response. For more information, see Connect REST API Quick Start.