Just did this myself today.
Take the rifle and set it in your lap with the front sight pointing to the left and the rifle upright. Next, take a flat screw driver and place the blade in the grove of the front sight as far to the front of the blade as you can (this would be all the way to the left while still being on the sight blade).
Next, with your left hand, push straignt down on the screw driver while being sure to keep it in the grove (this will compress the leaf spring). With your right hand, pull the sight blade to the right (towards the rear of the rifle). The blade should pop right out.
If you look closely, you can see a track path in the rear sight base. This is where the pins in the sight blade will travel. You can see by looking at the base, that the rear sight blade needs to move down and then back towards the rear of the rifle to follow the track. To see the track before removing the blade, you will need to flip the blade up out of the way to see between the blade and the sight base.
To reinstall the blade, push the blade back into the grove and push towards the front of the rifle. At the same time, push down hard on the front part of the leaf spring. You may want to put a rag between the your hand and the sight blade when pushing the blade back into place.
Note: Keep the sight blade horizontal in relation to the rifle when reinstalling it. It takes a bit of downward pressure on the spring and forward pressure on the sight base. You will hear a snap when the blade pops back into place. If the sight base does not want to snap back into place, use more pressure.