Okay, so you have a figure and you have some clothes and hair.
You can always select anything from the dop-down menu (top left of your stage viewport).

If the clothes are conforming, select the clothing item, then conform.
For the hair it might make more sense to smart parent it to the head. Select the hair, go to the Properties panel and press Set Parent, then select the figure head from the drop down menu.

Now everything should be set correctly, just pose the figure and you are good to go.

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