Setting up triggers

[GovindRulz]

Hi have been trying to replicate this , so that i can replicate something similar for my use case. but i have been stuck on the following part
"** and you'll need to create a method called /create this should be of type POST (enable CORS)
Make sure you enable CORS for this method. Now under Method Execution we need to set a mapping to get the right information into the lambda function from the front end. Create a new mapping with the type:
application/x-www-form-urlencoded**"

I dont see an option to add a method while creating a trigger. could someone help me out on this ?