From page 14 of the user manual:
# Take the Roomba off its base and press Clean. The lights should turn on.
# Press and hold Dock until the Roomba beeps and says the current language (about 3 seconds).
# Press Clean until you hear the language you want.
# Press and hold Clean to turn off the Roomba and confirm your language choice.
I have attached the full user manual for your vacuum below.
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