Arduino Software consists of two main components:

1: The Arduino IDE Software Development System that runs on your PC, MAC or UNIX system. You use this to write Software Sketches to make Arduino do what you want it to do. If you are just starting out, get and install the Arduino IDE as shown here:

2: Arduino Software Sketches that are uploaded to an Arduino Microcomputer board. This is the code you write to create the behavior you want in your project. It creates the actual "Machine Code" that runs in the Arduino to do what you want it to do. If you're starting out, you might look at the how-to pages HERE:

And,There are Example Software Sketches here:
And, very good Programming Tips from Nick Gammon here:
And, don't forget your Thanks! to Gavin Smith.

The official Arduino Software Reference is HERE. The entire reference is also loaded on your machine when you install the Arduino IDE. Click Help on the IDE.

Combining Arduino Sketches

This is often difficult. Here is an approach that may help you be successful: