Edit the tomcat-users.xml file which is in the conf directory under the Tomcat directory
Delete the lines with the comments around the last paragraph with the roles <!--
-->
Add at the bottom after the other roles (supplying a username and password you created) <role rolename="manager-gui"/> <user username="tomcat" password="s3cret" roles="manager-gui"/>
Save
Restart tomcat
Bring up the Tomcat manager at this location and log in using the userid and password you added to the tomcat-users.xml. (In the example above is it tomcat/s3cret)
http://localhost:8080/manager/html
and log in
You may want to undo this after you are done with the Tomcat manager as you will not need it regularly and leaving that section uncommented may get you tagged with a vulnerability