There are 2 things - 3 things - required to access the Tomcat admin webapps.
1. They must be installed (Some Tomcat versions do not include them in the base download).
2. You must have enabled a security Realm in the TOMCAT_HOME/conf/server.xml file. By default, no realm is available, but commented-out samples are present.
3. You must have roles defined and assigned to the admin user(s) - who, of course, also need to be defined.
Most commonly, people fail at item #2.
An IDE is no substitute for an Intelligent Developer.