Loading Sheet film into double dark slides
Remember before you start to make sure there is NO dust in the cut film holder, clean it at least 3-4 times, with compressed air, a paint brush or a vacuum cleaner, some photographers use all three.
In room light make sure the white or silver side of the clip on the top of the slide is pointing outwards( yellow arrow). As the other side is black, this silver strip is used as an indication the film is unexposed. It helps if you push the slide a short way into the holder with the light on.
In the dark take the film out of the box (often these boxes have three interlocking lids, some also have sheets of paper between the sheets of film some photographer have loaded the paper by mistake) and find the notch pattern of the film, this locates the emulsion side of the film. In relationship to the film holder, locate it where the blue arrow is.
Find the slots on either side of the holder (Where the red arrows point to) and push the film up through the retaining strips. It is very important that the film is located behind these strips or it can fall out and even end up inside the camera.