How are 6 "fixed" CO2 molecules joined toegther as glucose?
It's not really possible to break it down this way. The CO2 fixated by the RUBISCO enzyme generates two phosphoglycerate (2 x 3C) molecules from one ribulose bisphophate molecule (5C), while the rest of the Calvin cycle serves to regenerate 3 ribulose bisphophate from 5 phosphoglycerate. Hence, one 3-carbon sugar (glyceraldehyde phosphate or dihydroxyacetone phosphate) can exit the cycle for every 3 CO3 captured. The regeneration of ribulose bisphosphate involves several enzymes, and the stoichiometry is rather complicated; it would take an entire essay to describe it all. I suggest you look the calvin cycle in the metacyc database, it's a nice interactive resource where you can explore all the details of the reactions. Wikipedia also provides some details on these reactions.

The glyceraldehyde phosphate produced by the Calvin cycle is then converted to glucose and other sugars by the enzymes of gluconeogenesis. The key enzyme is fructose diphosphate aldolase (or simply "aldolase") which condenses glyceraldehyde phosphate and dihydroxyacetone phosphate to one fructose-1,6-diphosphate. A chart of the pathway leading to other sugars is found here.