When i use the construction set editor and want to add some sixy npcs I create some new npcs and give them the hair style(From rens beauty pack) that interests me most. When i Load the game it somehow resets itself to the monk head thats bald with a pony tail and has a blind on his eyes. Ive never been able to fix it and really want to know how. I know its possible Ive seen mods where people used the hair on the npcs. Many thanks if anyone has the answer.

You simply can't use the assets from one ESP in another without making the source ESP a master of your ESP. The default CS can only handle ESM mastering, that is ESPs as masters will get lost on save and with it any assets from other ESPs you used. Read up about "mod de-isolation" to this matter.

However, you can use Wrye Bash's function "ESMify" to switch an internal flag in the source ESP so it gets treated as an ESM by the CS. While this is the case you can open your active ESP and the source ESP in the CS, make use of its assets in your mod, and save without loosing the master information. If you then use "ESPify" to turn the source plugin back to normal your mod will keep the dependence on the source ESP. Just keep in mind never to open your mod without the source ESP being ESMified beforehand or the CS will again remove the master dependency and any contents thereof.

You can also just make "copies" of the assets you want to use, so they basically become part of your mod and will work without the source ESP. If it's just a few things you want to re-use, also give them your own EditorIDs and it'll be safe and clean. If it's a whole lot of content though, above descripted parenting is more advisable.

Or you could just use the CSE (CS Extender), as I've heard it allows for mastering ESPs as well directly.

Kia Ora

That it does,.. if you load your mod and ren's (or what ever mod your using assets from) CSE take care of the esm/esp issues
and the asset mod will become a master loaded with your mod,.. hope that as clear as mud mate

Seems like a lot of work but ill give it a go when i have the time.
Thanks guys.