The publicationID is the ID for a DPS 2015 project. You can find this in the browser URL when you navigate to the Content & Layouts section of the DPS 2015 portal and select the project that you wanted. The screenshot below the example that you mentioned in that help article illustrates this.
what exactly is the publicationID ? Is that the same as the iOS App ID ? My iOS App ID looks something like this "de.companyname.appname" but the one in the example looks very cryptic. Is it the same or is the pulicationID something different from the iOS App ID ?