inviting my elder sister and her daughter .

Well,l am an expect holding a Z visa in china my second year. l am here with my wife and kids and my wife as well holds a z type. We all carry Turkish passports and residence permit.

I would like to invite my sister (49)and her daughter(10) from Nigeria . I would be pleased if you guys can advice me on the necassry steps to take.
pls remember they carry Nigerian passports. Thank you all for your response in advance.