i have just purchased a refurbished apple iphone 8 plus during set up it was disabled, how do I enable it again to proceed with set up

You will need to restore the device using a computer. The process will erase the device. Later you can restore your data from a recent back-up. Instructions here…

If you forgot the passcode on your iPhone, or your iPhone is disabled - Apple Support

In this case, you will need to start set-up again.

You can't do it without a computer. Perhaps a friend with a computer could help or you could make an appointment at the nearest Apple store for assistance.

Apple Store - Find a Store - Apple