First and foremost, install bitcoin-core. I recommend compiling it yourself but there are binaries available for download. You'll want to perform all the steps in this tutorial - follow all steps for the daemon. Do not do the graphical user interface steps. https://bitcoin.org/en/full-node#ubuntu-1610
Run the daemon and use bitcoin-cli to familiarize yourself with the Bitcoin RPC API. https://bitcoin.org/en/full-node#other-linux-distributions
Start the daemon, such that it creates the right folders.
Stop it after a few seconds.
You should see a new folder
.bitcoind in your HOME directory. (Or AppData if you're on Windows). You'll need to add this file into it as 'bitcoin.conf':
Replace YOURUSERNAME with a username of your choice, same for the password. Remember these as you'll need it for configuring your NodeJS app.
Get the balance:
bitcoin-cli -rpcuser=YOURUSERNAME -rpcpassword=YOURPASSWORD getbalance
Pick a nice Bitcoin Core JSON-RPC Node module, like this one:
^Also has the get balance example.
They use the same commands that you enter in the bitcoin-cli.