"The women have dresses."
Translation:Les femmes ont des robes.
To know which articles to use in French, put the sentence in the singular:
The women ---> the woman: specific "La femme"
have ---> has "a"
dresses ---> a dress: indefinite "une robe".
Now, go back to the original sentence in plural and remember that the plural of "la" is "les" and the plural of "une" is "des".
The women have dresses = Les femmes ont des robes.
It is "les femmes" when you are either talking about all women in general or about all the women in some implied or overt group or situation. Now if those women that you are talking about have all the dresses that exist (again dresses in general or in some grouping of dresses) then you could say les robes. But when the women that you are talking about are not the only ones who have dresses you say "des robes". To summarize: "les x x x" is all inclusive. "des x x x x" = "more than one and less than all" implied or overt".