As the previous poster noted, without a solid model you can't make a 'real' detailed view. But you can make something kind of like one, in the same way that the DXF import is kind of like a drawing of a solid:
Having imported the entities on the left, you want to make a detailed view, which is 1) a set of entities of the same shape as part of the set of entities on the main view, 2) at a different scale, 3) that move together and 4) understand the difference in scale, so if you dimension the same entities on either scale view, you'll get the same answer. Here's what to do:
First, get the 2D View command into your toolbox, File>Options>Customize Ribbon>Commands Not in Ribbon>2D View (drag this up to your toolbar). It's greyed out, Tools>Legacy in drawing mode to enable it. Use this command to make a 2D view in the area you would like, give it a scale. A 2D view has a (purely cosmetic) outline and scale, and works like a regular view in that it moves its contents together, while leaving them individually modifiable, and that it understands a scale.
Second, in the Sketch tab, use Translate and Copy, then Scale, and possibly sketch a boundary spline and use Trim to remove the bits of entities that stick out. Use Relate to View to put the entities into the 2D view.
Ta da! One 'detailed view', ready for use! Note that it is not the case that changes to one will auto-update the other, but the set of properties (1-4) above will hold.
