Devices are physically connected to digital or analog ports on the Arduino. To associate them with nodes, you need to inform the node of the port number that you are about to use.
By a convention the leftmost pins are used to define the wiring information. If
the device is simple and communicates with the Arduino via a single hardware
port the corresponding XOD pin is called a
Note, that many devices require some specific hardware capabilities from the port they are connected to. Notably, to smoothly control a parameter (like LED’s brightness) the port should support PWM (pulse width modulation). PWM-enabled ports have a tilde (~) symbol printed next to their numbers on Arduino boards.
You can set port values exactly the same way as you do with other pins.