Problem Installing GFCI on a circuit breaker panel?

I am trying to install two GFCI breakers in my circuit breaker panel. The breakers I am removing only have hot wires connected to them (no neutrals connected to breakers). I removed them and put in matched amperage GFCI breakers. I reattached the load wires. I attached the coiled white neutral wires that came on the GFCI breakers to the neutral bar. However, when I power on the main panel, the GFCI breakers fault automatically. My question is, do I need to attach neutral wires to the GFCI breakers (load neutrals) even though the originals didn't have neutral wires coming out of them? What am I missing here? If so, how do I do that?