Here is what I do, Ariana... doing it this way because I don't really understand the tool, probably, but it works so:
I first try to load and conform the item using the provided morphs in the garment. Some of the time this works fine. However, I have had issues with it working correctly using existing morphs, so I do the following:
--Save your morphed target figure (your extremely morphed character) to a cr2 (in the figures library)
--Bring up the item of clothing you wish to make conforming to your figure in Poser File Editor. If you don't have this tool, get it (please). I consider it an absolute essential. Sure, you could probably do the same thing with other tools - feel free to suggest some, anyone reading this - but I just find it so easy to do with this and it's so useful for other things, there isn't a day I don't use this program.
--What you are looking for are morphs (FBMs and PBMs) that could interfere with with the morphs you used on your character. In PFE (or whatever tool you've chosen) delete those morphs both in the actor BODY:1 channels but also in the individual body areas that you morphed.
--I tend to run a "repair" sequence in PFE just to make sure my CR2 doesn't have any orphaned channels or dials or whatever.
--Save this file to a new name: [ jeans.cr2 saved as jeansClean.cr2 ]
--Bring up your morphed character in Morphing Clothes
--Select the morphs you wish to transfer to clothing. I tend to save the selection three ways: top and bottom and full so... CharlotteTOP, CharlotteBTM CharlotteFULL
--Bring up your cleaned-up clothing item you wish to put morphs into.
--Transfer them over, then give your newly-morphed item your character name: CharlottesJeans

--Load your figure and your morphed clothing and conform to...

I'd be delighted for Ralf to come into this forum and set me straight on a few things (features) I might have missed or am mis-using or whatever... but this method seems to work a treat for me, atm...

Monterey/Mint21.x/Win10 - Blender3.x - PP11.3(cm) - Musescore3.6.2

Wir sind gewohnt, daß die Menschen verhöhnen was sie nicht verstehen
[it is clear that humans have contempt for that which they do not understand] 

Metaphor of Chooks