every x second is under system events.. the cog wheel icon. It has to be a primary or secondary event, you won't find it under actions or not primary/secondary events.
I think from your post what your actually wanting is for the player to fire a single bullet by clicking and have to reclick for each shot... however you don't want them to be able to do it quicker than once per second... ?
If that is the case you will want to use a Boolean instance variable on your player, lets call it "hasFired=false". Now move your current Wait-1 to beneath the fire bullet action and add an action "hasFired=true" before it and a hasFired=false after the Wait.
On mouse click fire bullet
Wait 1 second
Add a second condition to Mouse click fire bullet (right click on,above or below the little green arrow on left side of condition space and select add-new condition)
that condition will be hasFired=false.
Now when the game starts the player can shoot by pressing mouse button because "hasFired" is false by default but once they click button and fire a bullet the flag hasFired will show true and clicking will not do anything but once a second passes it will work again because hasFired will again be false.