To get started you'll need to install dependencies with npm install.
In the builder.config.js file you'll find that the kovan network has been setup with process.env properties.
In order to fill these files out you'll need to create a .env file. This file will be ignored by the .gitignore so you don't accidentally commit up any secret variables!
In the .env file fill out the three values:
PRIVATE_KEY=0xabc...
INFURA_SECRET=abc...
INFURA_ENDPOINT=https://...
You'll need to grab a private key that has kovan ether in order to deploy on kovan. Then you'll need the INFURA_SECRET and INFURA_ENDPOINT from your infura account.
Once you have this setup, simply run npx buidler run scripts/deploy.js --network kovan to deploy to kovan!