May I suggest the following procedure for plugging?
Get your tablet and crush it as fine as you can in a mortar.
Using the disposable 10 ml syringe you bought at the pharmacy (pharmacies sell these in packs of ten for a pound or two) measure out a syringe full of water into a class.
Tip your powder onto a sheet of paper.
Using the paper as a funnel pour the powder into the glass.
Stir steadily for as long as you can.
Suck up the mix with the syringe.
Put a little lubricant on the end of the syringe.
Take some lubricant on your middle finger and smear it onto your anus. If you push out with your anus as if you were going to do a fart you will be able to get some lube on the inside too. Keeping rubbing your anus with lube until you feel it relax slightly.
Take the syringe and position it so that it can easily slide inside.
Push the syringe fully in while hooking your fingers under the projecting edge at the top end of the syringe. Push down on the plunger while holding the edges in your other fingers and then gently remove the syringe.
Go and watch TV for half an hour, try not to fart. I've seen a recommendation somewhere that you should lie down on your left side. This might be a good idea because that would help the liquid to run into the sigmoid colon.