missing documentation and example code: how to quickly and permanently change SPI clock divider

[shiftleftplusone]

missing documentation and example code: how to quickly and simply change SPI clock divider ? About setClockDivider(): "This function should not be used in new projects. Use SPISettings with SPI.beginTransaction() to configure SPI parameters."

But I don't understand how to use SPI.beginTransaction() or either function for AVR, and ARM, and ARM extended mode. More source code examples would be needed for this.