Associative Dimensions

I have a large assembly imported from another application. I have set the properties for each part, the assembly and the drawing sheet to inches.

When I try to dimension my drawing the dimension reflects the sheet size, not the actual model size. How does one make the dimensions in the drawing sheet associative?

I am new to SW drawing and I had planned on spending time getting up to speed, but I don't have time today, so if you could just point me the right direction for today, that would help greatly. I did try a forum search and the help files, but perhaps I am not using the correct SW terminolgy.

SolidworksDrawings And Detailing