It is not realy clear indeed

If you saved the material in the material room you just can load the prop/figure etc you mant to use.
In the material room click on the part (select it) you want to aply the material to and double click on the material icon on the right.
Now Poser should aply that material to the part you selected.

Oh and you need to be in the advancet settings of the material room.

Edit.
I just see that you talk about textures.
If the prop is UV maped, it needs specific textures for that part.
Using other textures might result in some weard effects.

I am not a complete idiot, some parts are missing :)

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