I am unable to open the tresure chests. Please help me. I don't know if I am standing in the wrong place or what.

All you have to do is stand in front of the chest, hold down the left mouse botton(or you can use alt), aim the yellow light on the lock that is on the chest until a symbil comes up and then let go of the mouse botton.

Press left mouse button or alt like Jackilyn said.

I'm not always stand in front of chest. Sometime besides it.

If not work (this already happen to me), try to restart the game, or move until alohomora spell shown.

If the other suggestions dont work-look into your input menu by pressing escape "esc" button while playing the game and changing the values for the wand.