I need some help with this..it`s my first time writing and not sure how to go about it.

I have a 4 month old daughter with my bf and along comes his 5 year old daugther with him. She`s a good child but her biological mother doesn`t care for her at all..basically neglects her. Her father spoils her and allows her to get away with murder due to him feeling bad for her. I agree with discipline and not being tought..but firm. Because he doesn`t want to look bad to his daughter, with the rules I tell him in regards to our house..he says for me to tell her. ie. not eating in the living room cause it`s me cleaning up after her. I only have these rules set in place because I expect the same from my daughter when she`s of an apprioate age. We have different values in regards to this as well. Slowly but surely wè`re getting there but I want us to work a team rather than indiviually. Any suggestions or tips....