The musician and presenter, 43, said it meant she had to be “the most mature you can possibly be”, even when she did not feel like it.
Klass, who is in a relationship with PR boss Simon Motson, has two daughters – Ava and Hero – from her previous marriage to Graham Quinn.
The former Hear’Say star welcomed a third child, with Motson, called Apollo, in August 2019.
Like Klass, Motson also has two children from a previous relationship.
Appearing on the Made By Mammas podcast, she said: “It really takes you being the most mature you can possibly be, even when you don’t want to be.
“I said to Sim when we were first all living in the house together, I said that I’m not going to tell your children off because I don’t feel like that’s my role.
“And within 10 minutes, that’d gone out of the window when one of them is hanging off the monkey bars and another is trying to put a ball through a window.
“In the end I just changed all that around and I sat them down around the table and said look, the only way we’re going to do this is, I see it as we’re all in a boat, this is how I view it.
“And one of you rocks the boat, we’re all going to feel it. And if one of you goes overboard, I’m going to grab you and make sure you’re safe.
“That’s the only way we’re going to get through it, is if we’re all in this together.
“If anything gets a bit rocky or if anyone’s in trouble, we all just say, ‘Remember the boat’.”
Klass also discussed teaching her daughters how to value money.
“My daughter has started teaching (music),” she said.
“So, I don’t give her any pocket money because I think that they get enough. Otherwise, it starts getting ridiculous, they have to learn the value of money.
“So she is now teaching and she’s got six pupils now. It teaches her time management, she’s got to be organised with it, she’s got to plan her lessons and she then has to manage her money.
“She’s got a little ledger, both girls get ledgers, so they know how to manage their money. I think it’s so important for women especially, to understand how to manage their money.
“As women, we’re often the ones that get left behind, we don’t want to ask for our pay rise, and we’re not always on top of our finances.”
Made By Mammas: The Podcast is hosted by Zoe Hardman and Georgia Dayton and is a Create Podcasts production.