How to draw lines only in Inkspace....without the fill

It seems like you either want to completely remove the fill on an object or give your object a transparent fill. Either way, you'll have to open the Fill and Stroke panel:

Step 1: Select the object in question.

Step 2: Bring up the Fill and Stroke panel. You can do this by pressing Shift+Ctrl+F or by opening the Object menu (just below the titlebar) and selecting the Fill and Stroke option.

Step 3: You will see a series of tabs on the top of the panel. Make sure the Fill tab is selected.

In order to completely remove the fill on the object:

Step 4: Directly under the row of tabs, you will see a series of squares, with an X and a question mark on either side. Clicking the X will remove the fill on the object. (Hovering over the X will show a tooltip of "No paint".)

In order to change the fill to transparent:

Step 4: On the RGB tab within the parent Fill tab, you should see four slider rows, with the letters R, G, B, and A in front of them. The A stands for "Alpha (opacity)". Either slide the slider all the way to the left or just set the value next to the slider to 0.

I recommend going through the Inkscape basic tutorial to learn how to do this and other things with Inkscape. To access the Inkscape tutorials, go to Help > Tutorials.