Context.xml file missing Tomcat 8

I'm a beginner creating a dynamic web project in eclipse, I need the context.xml file to set up a database realm but it's not under META-INF but I have found it in tomcat's conf directory.Have I configured eclipse/tom cat wrong because everywhere says the file should be in meta-inf? How can I add a context.xml file to my project? I am using Eclipse mars and tomcat 8.this is my first time developing for the web, so sorry in advance if this is a basic question.