# Authenticate with Salesforce Scheduler APIs

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.

:::note
It's not possible to modify an existing appointment via a guest user profile. You can use an integration user who has permissions to read and update only the required objects.
:::

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.