#1) You have to locate the blade release button on the saw (see your manual). The opposite side of the release button is a screw-like OVAL shaped PIN. To insert the blade, the direction( or position) of this OVAL shaped PIN has to match the OVAL shaped hole in the blade. You could use a screw driver to change the direction/position of this OVAL shaped pin. You have to push down the release button when you use the screw driver to turn.
#2) Hold the blade in Vertical position in your right hand. The "Oval" hole is on top. The teeth is facing your left hand. You will see that the "oval" hole on the top of the blade is a "horizontal" oval.
#3) Hold the saw (handle) in your left hand as if you were going to saw using your left hand.
Now peek through the hole of the saw and find the direction of the OVAL PIN. It has to be a "horizontal" (or lied down) OVAL. If it is not, use the screw driver to adjust it.
#4) Hold the blade using your right hand. Oval hole on top, teeth facing your left hand. Insert
the blade from the bottom of the saw. What you needed to do is to insert the PIN into the hole
of the blade. When you inserted the pin into the hole of the blade, slowly turned the blade upward, the blade will lock by itself.