Attempting to Run Script on Background Window

[TehCreepN1]

Title says it all. Here's the script I'm attempting to run (I am incredibly new to using AHKs and while I have SOME understanding I would appreciate any explanations being worded as if for a small child):

; MapleStory2 - A New Beginning
{}
^j::
Loop {
DetectHiddenWindows, On
SetTitleMatchMode, 1

ControlSend,, MapleStory2 - A New Beginning
loop, 26000{
Send, {Space down}
Send, {Space Up}
Sleep, 380
}
loop, 1 {
Send, {4 down}
Sleep, 750
Send, {4 up}
}
}
return