Co-parenting and accepting your SO children..

I'm torn I love my man and I know him and his kids are a packaged deal as I have my own babies from my ex husband-- so all together there's 4 kids but i don't know I'm so torn please don't bash me I love this man but I don't know how to "parent" his kids their mom is involved she doesn't care to meet me but knows I'm around his kids... my ex is in jail and we are divorced so don't ask questions about that- but I'm the "mom" in our home and it can be the smallest thing and my boyfriend will be like don't give that to (the kid-- I'm not saying the names for privacy) but I don't know how to coparent with their mom as she refuses to be cordial and talk to me

And my boyfriend says there nothing going on with him and the kids mom and I know their isn't I treat all our kids the same by the way I just don't know I haven't had to deal with this before...

Any advice on "coparenting"? Or how to deal with this

Thanks and as always be kind