How to make a custom hairstyle?

[LCYBC]

Greetings, I would like to ask how do you make your custom hairstyle...

I have got a hair model in nif

but I don't know how to import it into skyrim as a hairstyle properly...

Currently I am replacing hair mods with my hair but it comes with problems like messed textures

I used the texture from hair mod, and it looks good in Outfit Studio ( picture 1 )

and this is what it looks like in game... ( picture 2 )

and picture 3 is another hair from hair mod which is normal 

Please tell me what to do, I can upload my hair model if necessary, thanks