Lets see if i understand after reading about 30th times the manual

(dont laugh at me), i just need to make a player click a button during a pararell event to activate a switch, normally it would work just fine like this:
(works in a normal project whitout ABS)
but i cant use RMXP default input and disiabling BLIZZ ABS controls WONT HELP but to prevent player from using atacks, skills etc..
$game_system.blizzabs = POSSIBLE_VALUE
$game_system.attack_button = POSSIBLE_VALUE
$game_system.defend_button = POSSIBLE_VALUE
$game_system.skill_button = POSSIBLE_VALUE
$game_system.item_button = POSSIBLE_VALUE etcetera... or even this..
so i already read the "Utilities" and controls manipulation part but its not very explanatory in some parts like here:
1.- Use where?? in a call script? and by "Use" it means the player performs that action?
2.- How am i supposed to use the
Input.trigger(Inserting key) command to check if a button is being pressed :S
so far i got this as an example but i get errors:
All due my lack of scripting experience i assume but any help, hints of any kind would be GREATLY apreaciated, i already read the manual lots of times but there are missing bits of explanation for dummies as me