How can I use these playermodels?

[Melonne]

Hi, I came across superb playermodels
however they are divided into 3 models: the head, the body and the legs

how can I do to assemble them? I want to add that I do not know how the original creator uses them

Playermodels:

https://steamcommunity.com/sharedfiles/filedetails/?id=1637788424

Screens:
I would add later

[TheLightBringer]

You have to match the bones of the models with the bones in your base playermodel.