If you deployment has failed, then there may not be any well formed PetStore application to run. Secondly, the correct URL for accessing the petstore should be http://localhost:<port#>/petstore
I believe the "p" in petstore was left off inadvertently. Of course, replace <port#> with your appropriate port number for your web server installation.
I have just been through the same process. The application.xml files in the generated ear file have DTD references that point to external entities. If your installaion does not have internet access at deploy time then then these entites will not be visible.
There are 2 application.xml files. One is at the root of the archive. One is in META-INF. I expanded the ear, removed the DTD lines and re-jar'd the archive. (You could host the DTD files locally if you were keen but it is not necessary in this case.)