See: Chapter 5. Importers where we document the Import > Teiid Designer > Web Service Source >> Source and View Model (REST) feature.
The Web Service connection properties in the profile wizard allow None or HTTPBasic as options where the latter has user-name and password inputs.
Barry - Teiid Designer Project
The information you provided assumes a more recent version of teiid. These are my versions.
JBDS 7.1.1 GA
JBoss EAP 6.3 with Teiid 8.9.1 (AS 7.4.3.Final-redhat-2)
Teiid designer 8.3.4.Final
This combo does not have the additional features mentioned in the doc you provided. This thread mentions some correct version to try (https://developer.jboss.org/thread/253638) but 8.7 won't even start with EAP 6.3.Alpha1 as suggested so I am at a loss. Any guidence you or anyone on the forum could provide on installing a working version that correctly works with designer would be helpful.
Teiid 8.7 works with EAP 6.1.Apha
You'll probably want to upgrade to Teiid Designer Index of /jbosstools/updates/release/kepler/integration-stack/teiiddesigner/8.6.1.Final if using JBDS 7.1.1 GA. This version has been upgraded/tested with Teiid 8.7 runtime.