Schwinn pedal crank conversion

[dougsr.874]

I just bought the 4 cycle kit which includes a conversion crank unit for a 1 piece crank unit on most bikes. The bike is a 26" Schwinn Riverside. The problem is that the center for the new crank has no threads on it....so how do you hold it in the bike....The original crank has threads on both ends that hold the bearings and crank in place...I'll contact Jeremy if no one knows....