help (oneself) (to something)
To serve oneself (something); to take, consume, or indulge in (something) freely or without permission or restraint. There's plenty of food in the kitchen, so please, help yourselves to more. The vagrant they had given shelter to for the night helped himself to the family's prized set of silverware. The maps at the information kiosk are free, so tourists are welcome to help themselves.
Help yourself.
Please take what you want without asking permission. Sally: Can I have one of these doughnuts? Bill: Help yourself. Mother led the little troop of my friends to the kitchen table, which was covered with cups of juice and plates of cookies. "Help yourself," she said.