Pre-condition:
- You should generate pgp keys at https://pgpkeygen.com
- Download that keys 
- Install nodejs, npm (i'm using version v12.18.3 and 6.14.6)
- Unzip file pgp-tutorial
- Execute command: npm install
- Copy pgp keys into that folder 
- Execute command: node exampleEncrypt.js 

Flow:
- node exampleEncrypt.js (put your message)
- node exampleDecrypt.js (copy result of exampleEcrypt)

Document: https://www.npmjs.com/package/openpgp