If you are using an empty cassette from a roll of film, carefully, going around the rim in several places, pry off the cap that the spool doesn't stick out of with a bottle opener, trying not to bend it. Reloadable cassettes have caps that are made to be removed and replaced.
Remove the spool and with the extended part facing down, tape your film securely to the spool. I find it easier to cut off the leader so the end is square. When you take the film to be processed, it doesn't make any difference to the lab if the end of the film is square, and if you're developing the film yourself, you'll have to cut it off anyway to load it onto the processing reel. Make sure it's firmly attached to the film so it doesn't come off when you start to advance the film, and that it's firmly attached to the spool so when you rewind, you don't pull the tape back into the original cassette.
Slide the cassette back over the film spool, and if you succeeded in keeping the cap straight, close it. Note that the spool will now stick out of the end you removed, opposite the way a film cassette normally goes. If you can't get the cap back on, it probably doesn't matter. The point of putting it back in the cassette is to prevent exposure to any light that might leak through the winding hole.
An audible clicker let's you know that the film is advancing, and how far.
Place the film in the camera. If you're using an unexposed roll of film, be careful not to pull it any farther out of the cassette than necessary. On the take-up side, make some kind of mark on the internal divider where the sprocket holes ride over it. It's a little tricky to find something that will make a visible mark on the black divider, but I find it's sufficient to put a couple scratches with the tip of my Xacto knife.
Cut a narrow strip about 3mm wide from a plastic milk jug or similar plastic container at least 35mm long. Hold it against the internal divider with the bottom against the front of the camera, and cut it with your scissors as close to the divider as you can.
That should leave a bit extending above the divider a millimeter or two.
Trim the end so that it's narrow enough to go through the sprocket holes.
Carefully align it with the mark you made where the sprocket holes line up and tape it to the internal divider. It should just protrude through the sprocket hole. Once you have it in position, reinforce it with a few more pieces of tape to keep it in place.
When you advance the film, it should make a clearly audible click. A standard 36mm wide frame is 8 clicks.
You've exposed at least one frame loading the camera, so advance at least 8 clicks before starting to take pictures.
There is no way to count how many frames you've done. You're out of film when you can no longer advance the film.
The rewinding hole is in the bottom of the camera. (I usually cover this with a bit of cardboard between the front and back of the camera just because I'm paranoid about light leaks.) When you've finished the roll, in subdued light (not in full sun anyway) remove the winder, place it in the rewinding hole and rewind the film.
You should hear the clicker so you know when it's moving. Be careful not to pull that tape off when it stops. Remove the film from the camera, and remove the take-up spool. I usually leave a bit of film sticking out of the cassette to make it easier for the lab to process it.
As always, please let me know if there are any questions or comments.