the examples i have found requires me to use #include, and i'm not sure how that will work when i unplug arduino from the computer
#include is a pre-processor directive. It tells the pre-processor to copy the contents of the file at this point in the code. Once that happens, the compiler parses the code, and generates a bunch of object files. Then, the linker is invoked to combine the object files into a hex file. That hex file is uploaded to the Arduino.
When the Arduino executes the code, it does not need to access the PC where the included file was stored.