I need to adding the cost of a capital improvement to the basis of a rental property for depreciation purposes. I can add it as a new Asset but it does not accumulate to the same rental property. I am looking for the way to correctly do this.
You mean attach to the same property. You can change the activity in the Forms menu, while you are looking at the new asset sheet.
Every time you add a new asset, do it while looking at another asset in the same activity, then it will attach properly.