activators:

for buttons that are on the GBA (A,B,L,R,start,select, up, down, left, right), to add one the first line of the code would be something like:
Code:
94000130 XXXX0000
XXXX will be the activator code based on the button(s) selected to use. An easy thing for that would be downloading DSWorkshop, but you can also look at the bottom of this page of the wiki: here

NDS buttons (X and Y) have activators starting with:
927FFFA8 instead of the 94000130


at the end of the part activated by that (generally, but not always, the end of the code) you need to add a terminator:
Code:
D2000000 00000000
that line needs no modifying, just put it in as is like that.