Getting my children on a schedule....

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I have two children a 2.5yr old and a 4month old both girls. Currently they run the show! My toddler goes to bed whenever she wants, eats breakfast, lunch, and dinner whenever she wants pretty much does whatever whenever. Today was the last straw! I'm sick of being so tired and run down! My house is a f***ing mess and it drives me crazy!!!! I'm losing my mind! I need to get my children on a schedule (naps, feeding time, bed time, pretty much everything) 
I'm looking for help on where to start with that. I have no idea on what a good schedule is and how to go about using one. Anyone with advice please help me