Ok, Welcome to Construct 2. It's nice to finish the tutorial first.
In the page 5 of the basic tutorial, you can see :
Condition : Left mouse Clicked
Action : Player spawn bullet
Make sure that 'Set angle' to 'Yes' in the bullet behavior properties.
(and you can give the value 'off' to 'Set angle' option and try again to see the difference.)
You can modify it like this for the triple shot.
Condition : Left mouse Clicked
Action : Player spawn bullet
Action : Player spawn bullet
Action : Bullet set angle (bullet.angle - 15)
Action : Player spawn bullet
Action : Bullet set angle (bullet.angle + 15)
It's related how to 'Pick' something. 'Picking' is so important when you go deep into C2, so you may check another tutorial or forum threads about this.