The Time Stamp service is offered in the form of web services integration :

The Time Stamp is a service that is designed to be used by the various applications or services offered by public administrations. In this sense, in order to make use of the service, it is necessary to carry out an integration between the application or service of the user administration and the Time Stamp. The Time Stamp has a messaging protocol that defines how business requests should be and allows you to interpret service responses.
This modality requires technical resources from the entity to develop web services. To facilitate the integration work, the following documentation is provided:

Related content:

In what state is the registration of the Time Stamp service?

Self-executing Adobe security configuration package

Do I need to authenticate with a time stamp certificate?

Integration documentation - Validator and Time Stamp