To install the feature from the command line, type: bin/installUtility install com.ibm.websphere.appserver.org.eclipse.microprofile.rest.client-1.0
If you are installing into 8.5.5.5 or earlier and the feature supports that version, use the featureManager command, for example: bin/featureManager install com.ibm.websphere.appserver.org.eclipse.microprofile.rest.client-1.0 --when-file-exists=ignore