As a plugin developer you can use this plugin as dependency of your plugin by adding a dependency tag to your POM.
To add the latest version of this plugin as a maven dependency, use the following:
<dependency>
<groupId>com.cloudbees.jenkins.plugins</groupId>
<artifactId>additional-identities-plugin</artifactId>
<version>151.va_d0a_78e6c31f</version>
</dependency>