Newbie needs help with tutorial 3.5

#===============================================================================
# Skill Self Effects
# By Jet10985 (Jet)
# Requested by Touchfuzzy
#===============================================================================
# This script will allow you to specify a skill's effects tot arget the user
# instead of the target, on skills that don't already effect the user.
# This script has: 0 customization options.
#===============================================================================
# Overwritten Methods:
# None
#-------------------------------------------------------------------------------
# Aliased methods:
# Game_Battler: item_effect_apply
#===============================================================================
=begin
To specify the effects, use this notetag in the skill's notebox:
<self effect: 1>
or
<self effect: 1, 2, 3> to specify more than 1 effect
--------------------------------------------------------------------------------
Use of this script could be as the following.
You make a "Berserk Strike" skill, which does 200% damage to an enemy.
You make the 2nd effect "Defense Down 50%" and want it applied to the user.
You'd use this notetag: <self effect: 2>
=end
class RPG::Skill
def self_effects
if @self_effects.nil?
@self_effects = []
self.note.each_line {|a|
scan = a.scan(/<self[ ]*effect[ ]*\:[ ]*(\d+(?:[ ]*,[ ]*\d+)*)>/i)
begin
scan[0][0].scan(/\d+/).each {|b|
@self_effects.push(@effects[b.to_i - 1]) if b.to_i >= 1
}
rescue Exception => e
end
}
end
@self_effects
end
end
class Game_Battler
alias jet3745_item_effect_apply item_effect_apply
def item_effect_apply(user, item, effect, reffed = false)
if item.is_a?(RPG::Skill) && item.self_effects.include?(effect) && !reffed
user.item_effect_apply(user, item, effect, true)
return
end
jet3745_item_effect_apply(user, item, effect)
end
end

Scenario: I want a skill to add an effect on the user e.g. exhaustion.Not too hard.

a.add_state(2); a.atk * 4 – b.def * 2

Could also have it damage the user etc