After displaying the list of publishers, select a publisher such as Public Library of Science or Hindawi. A list of journals from that publisher that are accepted for JCR tracking appears, usually in alphabetical order.
You can click on one journal title to see its JCR data, but the most useful comparative step from the journal’s title page is to go the the View Journal Summary List, which will show the subject category for the journal, with the ability to rank the subject by comparative measurement like impact factor.
For instance, I went from Public Library of Science to PLoS Medicine to the Medicine, General and Internal subject list, which when sorted by Impact Factor showed PLoS Medicine to be ranked sixth in impact factor. There is a video explanation of the Impact Factor from ISI: