While installing Netbeans IDE it is install GlassFish server and Tomcat server if you customize it. But if you have only GlasFish server or would you like to have another tomcat server you may do it very simple.
First download tomcat server from http://tomcat.apache.org website. I describe it in my post: How install and configure Tomcat 8 on windows ?
If you install and configure tomcat server, choose from menu in Netbeans IDE Tools->Servers.
In Servers window click the Add server buton.
From Server list choose Apache Tomcat or TomEE element and in Name field write your any name, mine it is Tomcat 8.
Click the Next button. You see Add Server Instance window.
Choose server location, clicking the Browse button. It is path to your installation place of tomcat. In Username and Password write data configure in your server in conf/tomcat-users.xml file.
Click the Finish button. In Server window You see in Connection tab your configuration data.
Click the Close button and work with new Tomcat 8 server.