Locate the Tomcat-user.xml file in the Conf folder in the Tomcat folder, open it with Notepad, and at the bottom you can see that Tomcat has commented out the user by default, that is, opening the Tomcat homepage is not going to manage the page.
Here's how:
Found it
<!--
<role rolename= "Tomcat"/>
<role rolename= "Role1"/>
<user username= "Tomcat" password= "Tomcat" roles= "Tomcat"/>
<user username= "Both" password= "Tomcat" roles= "Tomcat,role1"/>
<user username= "Role1" password= "Tomcat" roles= "Role1"/>
-
Remove the top <!--and the bottom
In <role rolename= "Role1"/> This line add <role rolename= "Manager-gui"/>
Added after <user username= "Role1" password= "Tomcat" roles= "Role1"/>
<user username= "Manager" password= "Your Own password" roles= "Manager-gui"/>
Restart Tomcat, go to admin page, user name: Manager, password: your own password
apache-tomcat-7.0.70 Unable to access Manager Admin App Project