don’t bother- it does not work in terms of sealing puncture
the powder inside the tube stops the Stan’s from coagulating when a puncture occurs
I’m afraid that is rubbish, it works perfectly well, as well as tubeless tyres as far as I can tell.
To get the stuff in you will need a syringe that will hold 40ml. Widen the nozzle so it fits securely over the valve.
If you have schwalbe tubes then the valve core will unscrew completely leaving a schraeder style valve opening behind.
Otherwise you will need to unscrew the valve locking nut thing all the way off the valve stem (talking about presta here) until it comes right off, you might need pliers to unscrew it as they are not designed to come off, but they will.
Then carefully feel through the tube the valve and let it fall into the tube, try to hold on to it, but don’t panic it you lose it, you will find it again!
Squirt some gunk into the tube and then by feel push the valve back into the stem and replace the locking nut thing on the end.
That said I would still carry a tube, sometime, whatever you do, you will ride over something that will make a hole that wont seal.