because all this is explained, albeit if you read sufficiently far
back into previous discussions.
If you can get a little finger into the opening, then that is what you use to stretch to start with, always swapping for the largest finger - or combination thereof - that you can insert.
The trick is in getting the finger(tip) in through the opening, so that it passes all the way through the tight part and sits beside (or above) the glans. You have no hope of doing this while the foreskin is sitting on the glans, so you have to stretch it out as in that picture,
away from the glans so that it is a smooth "tube" into which you can slide your finger
while you hold it on the stretch. Three hands would be a distinct advantage if you can find a spare.

I am
impressed! Where did you find a doctor with the competence to prescribe you an actually
appropriate cream (though the ointment form would be preferred)?
You are correct - you do
not want it on your glans as far as possible (though it isn't really fatal), in fact anywhere but the tight part so you do not want to apply it until
after a stretching session because you do not want it to be spread further by the stretching procedure.
To apply it only to the tight part, you can either do so while you "funnel" the foreskin (gripping as far
inside the opening as possible by "rolling" it back in your fingers) - that third hand is invaluable in this case - or else you may just pull the foreskin back as far as it will so that the tight part is caught at the tip and hopefully, some of the inner foreskin pushes out through it, and applying the cream to where you see the tight part. Use no more cream than rubs in and disappears - if it feels "greasy" afterward, you have used more than necessary.