Building Web Application in Eclipse

Download the tomcat installable from https://tomcat.apache.org/download-80.cgi

​and follow installation instructions (for mac you just need to download the Zip file and unzip it in a location you are unlikely to delete)

In the bottom panel find the Servers tab

If you don't see the servers tab, you should be able to find it through Window->Show View-> Other->Servers

Right click in the Server tab on an empty area and select New->Server

Pick Tomcat 8.0

Next to Server Runtime Environment click Add->Browse and navigate to the location you stored the tomcat8 in
Click Finish, and Finish on the parent window

To build a simple web application, go File->New->Project->Dynamic Web Project

Give your project a unique name and select Tomcat8 as a target runtime

Drag your new project onto the tomcat server and restart the server

Click on the Web Content folder of your project then go:
File->New->File-> index.html
this will create an empty file under the Web Content folder
click on the file and Enter some text, then save the file. 
You should now be able to access your application on your localhost server