Arduino programming basics
Begin with setup, loop, named pins and small, verifiable changes.
Understand the sketch
setup() runs once when the board starts. loop() repeats. Begin with a bundled example for your exact board and change one behavior at a time.
Use the board reference
Pin names, voltage limits, timers and memory differ between boards. Consult the exact board reference before wiring. Compiling successfully does not prove a circuit is electrically safe.
Read the first useful diagnostic
Verify the sketch, then inspect Problems or Build Output. Fix the first useful error and compile again; later messages can be consequences of the first mistake.
Learn from working examples
Open a tutorial to study its code, named connections and expected behavior. Library examples use the pinned version shipped with Circuitera.