Timing Chain

I am putting my Gen 3 Prius back together after replacing the head gasket.

I am installing the timing chain and I notice a slack in the timing chain. The chain lines up with 2 of the 3 indicator points among the chain the cogs. One of the cogs seems to have rotated off just slightly. Enough that the chain can't set correctly. My apologies for bad terminology and nomenclature, but how do I move the crank arm or cog so the chain seats properly?