Advanced Custom Fields (ACF) allows you to create custom Options Pages in WordPress. These values are stored in the WordPress wp_options table.
The WS Form #option_get variable allows you to retrieve values from the wp_options table. It can be used in actions such as Send Email, Webhook and other integrations.
The syntax is:
#option_get("option_name", "parameter/key")
For ACF, the option_name parameter is prefixed with options_ when a custom field is saved from an Options Page.
So, for example:
Field Label: API Key
Field Name: api_key
The option_name would be: options_api_key
Therefore to get that value using #option_get, you could use:
#option_get("options_api_key")