First of all starknet is still in alpha, that's why codes can be changed often.
So, we need to have a node and npm is included with Node.js.
If you need to download it, you can check the Node.js website.
Version of node: v21.1.0 Version of npm: 10.2.3 Version of starknet: 6.13.0
For changing the version of npm...
npm install -g npm@10.2.3
After installation of Node.js, let's open the terminal again and create a folder where you want...
# For example on desktop
mkdir How-to-use-Fibrous-SDK && cd How-to-use-Fibrous-SDK
Install the fibrous-router-sdk with using terminal...
npm install fibrous-router-sdk
Install the starknet library with using terminal...
npm install starknet@6.13.0
Install the decimal.js library with using terminal...
npm install decimal.js
For the Examples, please refer to the next step.