By 1952,many scientist were convenced that genes are made of dna, but they did not yet know how dna worked. why was it important to determine the structure of dna to understand how dna stored, copies, and trabsmitted information

Once they understood the structure of DNA a lot of things became more clear including how DNA was replicated. 

So I think your answer is copies? meaning how it is copied (replicated).

The structure also led later on to how it was transcribed into mRNA (and eventually into proteins by ribosomes). 

Rna polymeras should attache to the promoter.