Sure, here is a step-by-step tutorial for installing Fider on Elementary OS:

1. First, you need to make sure your system is up to date. Open the terminal and run the following command:

   sudo apt-get update && sudo apt-get upgrade
   

2. To install Fider, you will need to have Node.js and NPM installed on your system. If you don't have them already, you can install them by running the following command:

   sudo apt-get install nodejs npm
   

3. Once you have Node.js and NPM installed, you can proceed with installing Fider. Start by downloading the latest version of Fider from their website (https://fider.io/download).

4. Extract the downloaded archive. Open the terminal and navigate to the directory where the archive was downloaded. Then, run the following command to extract the archive:

   tar -zxvf fider-*.tar.gz
   

5. After the archive has been extracted, navigate into the newly created directory:

   cd fider-*
   

6. Now, you need to install the dependencies that Fider needs to run. Run the following command to install them:

   npm install
   

7. Once the dependencies have been installed, you need to configure Fider. Copy the sample configuration file:

   cp .env-sample .env
   

8. Open the newly created .env file in a text editor and configure the settings to match your setup. You will need to set the DATABASE_URL and SECRET environment variables.

   # Example database URL (replace with your own)
   DATABASE_URL=postgres://username:password@hostname/database
   
   # Example secret (replace with your own)
   SECRET=my-super-secret-key
   

9. Once you have configured the settings, you can start Fider by running the following command:

   npm start
   

10. Fider should now be running on your system. You can access it by opening a web browser and navigating to http://localhost:3000.

Congratulations, you have successfully installed Fider on Elementary OS! You can now use it to manage feedback and suggestions for your projects.