1 Make sure your spiral is completely dry. It is not possible to load film onto a spiral that is even so much as damp. You may have found this out already. Check that there is nothing stuck in the grooves. Emulsion can be stripped of the edge of the film during loading/unloading so rinse the spiral thoroughly after use.
2 Trim the leader off your film. If you are lucky/careful when you rewind your film the leader will be left sticking out. It is the curved bit at the start of your film. You want to remove this bit and be left with a slightly rounded end which is easier to feed into the spiral. Cut between the sprocket holes as you do not want any bits sticking out to catch on the spiral . If you do not have the leader sticking out you have two options.
a) open the cassette, which you may already be doing. Remove the top from the cassette and slide the film out , try to keep the film from unrolling at this stage. Trim as above.
b)Use a film leader retriever to pull the leader back put of the cassette. You can get one from a camera shop.
3 Load film. Gently feed the film onto the spiral.If the film is still in the cassette pull out a couple of inches, if you had to remove the film you will probably have to let it go now. Try not to let it drop to the floor as it will get covered in stuff.You will now have about four feet of film swinging about which makes things very awkward particularly if you are not very tall. You could , if you have a clean surface to work on , just let the film drop a few inches on to that. If you are using a Paterson type spiral with the ball bearings at the start you just have to feed the film over the ball bearings until the sprocket holes catch on the bearings.
If you are using a Jobo type spiral you will have to apply a little pressure with your thumbs onto the edge of the film to hold it. There is a groove kinda thing just where the film goes in.
4 Wind the film on. With the Paterson spiral this is fairly easy. If you still have the film in the cassette you can pull a fair piece out now. Hold the spiral in both hands and rotate alternate sides back and forth .Don't push the film on ,wind it on.
With the Jobo spiral when you rotate one side release your grip on the film edge on the opposite side.
5 Take your time. Don't try to rush the film on. If both film and spiral are dry and you took care when first loading the film in, making sure both edges of the film are in the same groove on the spiral the film should go on fine.
6 Trim of the end. When you reach the end cut the film leaving any tape that was holding the film on the reel.
7 Put the film in the tank. Slide the spiral over the centre spindle, put it back in the tank and put the lid on securely.
8 Disaster. Don't panic.If you feel you are forcing the film it is stuck , if it makes crunching noises it is stuck ,if it is coming of the spiral somewhere other than where it goes on it is not in right. Just stop and slowly pull the film back out. Sometimes just pulling a few inches back out then trying again works fine if it was sticking. Likewise sometimes gently squeezing the sides together a couple of times can also free of a sticking film .
If the worst comes to the worst you will have to take the film of and start again. If you had to take the film out of the cassette this is a pain because you are now stuck in the dark but if you were able to keep the film in the cassette you just have to wind it back in put the light on and then the kettle and try later.