Shimano created Biopace with the completely wrong orientation of the biggest radius of the oval. Instead of positioning it in power zone which is slightly below the level of the crank, they clocked it to the dead zone where human generates least power. The result was that in power zone pedaling was too easy and in dead zone very difficult. Exactly opposite to how it should be.

Position the crank between 3 & 4 o’clock (largest part of the chainring will face up) and then tighten the chain the same way as you would on a round ring.