Office 365 is the brand name Microsoft uses for a group of software and services subscriptions, which together provide productivity software and related services to subscribers. It covers cloud storage, office products, email services, etc.
The online version of Office 365 is not supported with Read&Write 6 because it is a cloud based application.
Office 365 subscribers can download & install Office 2016 to their machines and use it with Read&Write 6 however.
You can find the Microsoft article for instructions!