Phew... okay...I'm really sorry. What does this mean:
Send...a packet terminator, like carriage return (which the Serial Monitor can add for you).
And:
use atoi() to convert the array to a number, and use the number.
What class does that function apply to? Or else what does the method atoi() do? I couldn't find it on the reference page.
Anyway, I'll try to figure this out myself but I'd be mighty greatful if someone could give me the code or a link to a similar code.