How to navigate and use the Load Contours tool set

I have yet to find information on how the Load Contours tool set works. There are some videos out there, but I've not seen details on how selection of entity types, layers, etc. and the ADD FILTER digitizing/selection tools work together. Where does one start? How do they work in combination? When I click on a contour line from a .dxf file I get an error response that "The filters you have selected do not contain any lines which you can import". I have actually imported them once but have no idea how I stumbled on accomplishing that.

Perhaps someone can steer me toward to that portion of the user manual (which I have open on another screen during the process) or a video tutorial that will guide me through the steps and explain how it works.

When I click on Add Plans from Site Plan or File, I get the Load Contours dialog box. When I click on New Filter as required to get started I'm automatically in a GUI ADD FILTER box where I have to use a cursor to select as many lines of the type I want to extract. As soon as I click on the first contour I'm told that the filters you have selected do not contain any lines which you can import. As I previously stated, this worked once, somehow...  And now I have the option of selecting options under Entity Types, Layers, Colours, etc. So, I select Lines as the Entity Type and both the major and minor contours under Layers. And nothing happens and I have no idea of what to do next. Item 4, Elevations from the manual is apparently beyond my understanding. There is no information to provide context on what the Not Set values mean or how to use it. I don't need to crop the plan or do any Modifications. In the Original, I hide all layers that aren't the major or minor contours which makes it easier to see those two layers. And I click New Filter to activate the selection cursor, click on a minor contour and am yet again told that there are no lines that I can import. I click export and do so, then Sketchup is launched... I click on Finish and a file that I thought was stripped of everything but contours appears and I looks like I have to start the process yet again.

There's got to be a clear description, written or video tutorial, on how this is supposed to work but I have yet to find it. If there weren't so many people who find this software helpful and fairly easy to use I'd drop it and move on. There's some basic thing I'm missing and hope somebody can point me in the right direction.

All the best,

Tom