Since I doubt you entered the property as 2 separate assets to begin with you will now need to do so to split them up.
First take the asset out of service by converting it to personal use as of the first of the year. Then take 1/2 of the basis that was being depreciated and enter each side as a new asset with the same start date you already used and 1/2 of the prior year depreciation.
Then convert that new asset you now live in to personal use as of the date of conversion.
