Will Office 365 ProPlus work with my copy of Office?
Installing Office 365 ProPlus will not overwrite the existing Office suite. You can have
an earlier version of Office and Office 365 ProPlus installed on the same computer.
If you do not want to use the earlier version of Office you may uninstall it by going to control panel, programs and features list.
For more information about having multiple versions of Office on
the same computer see this