Up the butt

How far do you want it to go? Usually when you insert it, it sort of "slips" into place just past the rectum.

I don't have particularly long fingers (a disadvantage for a musician!!) but I push it in as far as I can, which is likely around an inch, and then work the sphincter muscles to further help it in; it feels as if it slides into "the right place." If I haven't pushed it in far enough, it comes back out and I repeat the process.
When sore, I, too, lubricate it with something. And when flaring, there is momentary pain as it slides into place, but that goes away in a few seconds as the canasa begins to melt.

One can look up how long the anus is, but what is confusing you..?...

Rod

You push it past the sphincter. You'll know where that is if you insert the suppository and squeeze your butt (kegel squeeze) and the suppository will kind of be pushed into place.

q