Use the LEFT and RIGHT, or [ and ] keys, or type an ID number, to select a 16 color palette.
Or press P or click on "Pal ###" to browse for a palette.

Overwrite Current Palette: overwrites the current palette with the one from the image.

Remap into Current Palette: this option is available if all the colors in the image exist in the selected palette, but in a different order, or with extra colors. This allows the image to be imported perfectly.

Import Without Palette: don't change the palette at all. When you select this option the resulting image is previewed.