Rest API

I have the following scenario.

The customer has two domains.
One for his website and another one for his shop.
Let’s assume the following domains:
Website: example.com
Shop: shop.example.com

When someone place an order on shop.example.com he can also subscribe to the newsletter which is send from example.com.
So the task is to add the subcriber programmatically.

I already found out that there is a REST api but I couldn’t figure out how to access it.

The first problem is that I don’t understand which URL I have to call.
ON https://www.thenewsletterplugin.com/documentation/api-reference/#/subscribers/put_subscribers__email_ I see a URL /subscribers/{email}.
Does this mean if I want to add [email protected] the url is /subcribers/[email protected]?

Could you give me an example how to do this using PHP Curl.

Kind regards

Alexander Behling