Cannot find module 'alexa-sdk' about skill-sample-nodejs-adventure-game HOT 1 OPEN

I am also a beginner, but I finally got it to work. Here are the steps I took:

Download and install the latest version of node.js
Go to https://github.com/alexa/skill-sample-nodejs-adventure-game and download the zip file
Extract this zip file into folder of the same name
Open a command prompt and navigate to the subfolder lambda\custom
In the command prompt type "npm install --save alexa-sdk"
lambda\custom now contains a folder called "node_modules"
Within the node_modules folder, delete "aws-sdk" because it makes the zip file too big
Now zip the contents of lambda\custom and upload this zip file into Lambda
make sure index.js and all the other files of lambda\custom are placed in the root folder of your function
Also make sure that the APP_ID is defined under environment variables
Do a test of the function as described in the tutorial

from skill-sample-nodejs-adventure-game.