This guide simply explains how to flash an "ino" sketch on your Arduino Uno/Nano or similar, using Arduino IDE. For this guide, I used a chinese Arduino Nano clone equipped with CH340 USB-to-UART adapter. This guide is also applicable for flashing Fuelino software into Fuelino hardware (such as Fuelino Proto3).
Before performing the following steps, Arduino IDE should be already installed on your PC, and also you should have installed the drivers for communicating with Arduino via Serial communication (CH340 drivers in case of Arduino Nano Chinese clone used for Fuelino). These drivers are widely available by searching "CH340 drivers" on Google.
Step 1. Obtain the sketch to be compiled and flashed. In case of Fuelino, download the latest Fuelino sketch from here. Extract the content in the Documents/Arduino folder of your PC. The following folders should be extracted: "arduino_efi_nano" and "libraries".
The compiling process might require some time, depending on your PC. It might take 30 seconds - 1 minute. At the end, the following message should appear: "Done compiling". The Flash (ROM) size, and RAM size used for global variables are shown.
Step 6. Now we are ready to perform the program flashing into Arduino (Fuelino). Click on "Sketch -> Upload". It will take some time to flash the software, proportional to its size in bytes. In case everything was done properly, the following message should appear "Done uploading".
That's all. In case you are using Fuelino, now your software is running inside Arduino Nano, and you can try to connect to it by using the Fuelino Calibration Tool.