The Submodel Service Client is intended for interacting with a Submodel Service conforming to the Part 2 specification of the IDTA.
It can be included in your project by adding it as an dependency to the pom.xml:
<dependency>
<groupId>org.eclipse.digitaltwin.basyx</groupId>
<artifactId>basyx.submodelservice-client</artifactId>
<version>2.0.0-SNAPSHOT</version>
</dependency>
Please note that you may need to add a new repository in the pom.xml to access the snapshot repository as documented here.