https://www.tutorialspoint.com/arduino/index.htm
Complete tutorial how to program arduino.
https://www.youtube.com/channel/UCfYfK0tzHZTpNFrc_NDKfTA
Several videos teaching how to use and program Arduino. It also teaches some electric concepts.
https://www.arduino.cc/en/software
To program your Arduino board you would need to install Arduino IDE. It is available for Windows, Mac OS and Linux
https://www.tutorialspoint.com/cprogramming/index.htm
Complete tutorial to learn to program in C.