How to use RawTherapee to get my RAW (NEF) pictures to a decent state?

As below, the preview shows a great photo (looks like the processed JPEG from the camera) but after I double click to edit, it goes to the "raw" image which is washed out and I can't seem to get it back to the "nice" image of the thumbnail.
Added (1). I guess I can only show one photo… But you can see the nice thumbnail of the far right image… As soon as I double click it becomes washed out and I don't know how to get back to the nice preview or how to get the nice preview to show up in the large screen (these are all NEF files).
Added (2). I'm very new to post-processing images (pre-beginner, if you will). Clearly RawTherapee can process the images to a "base" (as seen in the thumbnails)… I can modify that "base" image to change it as I like, but my problem is that I don't know how to take a completely raw image (which is what it seems to be giving me once I choose it) to a reasonable one.

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Why do I get this double imagining effect when I film on my DSLR?

So I'm currently filming something for my uni project and this point was picked up upon. I'm using a Nikon DSLR, although don't know why this happens and how to change it?

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