You need to remover the "cap" on the end of the spindle.
There will probably have a set screw on the back side of the quill, that keeps the cap from turning,remove that first.
Next the cap will screw off. Be aware that a lot of them are left hand thread. Just depends on the machine.
Use a strap wrench to remove it.
After you remover the cap, you will see the collet indexing pin hole. It will have a locking set screw, a 1/2 set screw if you will.
Remove that and then you can remove the indexing one.
They can be a bear sometimes as they get smashed over and don't want to unscrew. You may have to use a small file to reach up into the spindle and clean it up before it will come out.
Good luck. Hope that helps.