Digispark Attiny85 sleep and auto wake up

Hi, I want to make my attiny85 sleep for 10 seconds and auto wake up for 10 seconds, this process is continuous. For every wakeup, the built-in LED will turn on and vice versa. Can anyone help me to write the code in Arduino IDE? Thank you.

This is the definitive guide to sleep modes with AVR microcontrollers such as the ATtiny85: https://www.gammon.com.au/power

A ten seconds sleep has to be made up of a 8 seconds sleep followed by a 2 seconds sleep because that is the way the watch dog timer works.

Try to put some code together so you can base your next questions on that.