Click on the "+" button to add the files to be converted. All supported formats can be selected at same time and will be converted in a sequence of files starting with the generic name you've specified just below. Created file names will be in the form Name_XXX, where XXX is the number of each image in the sequence. The button "Demosaicing" must be unchecked int order to convert RAW files into CFA (Color Filter Array) monochrome FITS pictures, a necessary step to pre-process DSLR images.