After reading the tutorial you linked, my first suggestion would be to raise the size of your ennemies to 10X10 px and use the rts behavior. This will be the quickest, less painful way of doing things. ^^
Else, if you really want to handle A* as construct's events...
For starter, be sure that the hotspot is in plain center of your sprites.
Your depart will be your ennemy sprite, the target is your player sprite.
So ennemy.X and ennemy.Y are your first node.
Save its position to an array that will act as your open list (prepare also an array that will be your closed list and another array in which you may save F,G and H)
To find adjacent nodes you add/substract 5 to your actual node's X and Y to find the center point of your next node.
From there, follow the steps of the other tutorial.
You'll have to set and test F, G and H's values (as described in the tut).
To adapat the manhattan method you'll have to determine its position in relation with the current node (is it on its right? on its left ? up ? down ?...) and apply the correct calculation.
Using the example in the tutorial target node is right ahead from depart node.
So the calculation would be: H = ((Target.X - Ennemy.X) / 5) * 10
(The distance between the X is "reduced" to the number of nodes between Target and ennemy(/5) and then the cost is added (*10). 5 here is your node width.)
The calcul would be different for each direction.
Lets pretend the target is one case above than in the tutorial.
Calcul would be : (((Target.X - Ennemy.X) / 5) * 10) + (((Ennemy.Y - Target.Y)/5)*10)
Then make sure that 5 pixels around your next node's center there is no object making it "unwalkable". Save its status to the correct array (open or closed list).
Depending on your level of confidence and ability with Construct this might be hard to realize.
If it too much, by all means, stick to RTS behavior. This will be the simplest and most effective way to do.
This answer is by no mean comprehensive but it should helps you get started if you really want to handle codewise.