trying to run excel (Office 2016) this because need to buy license?

happy to pay for licence so I can gt this working i.e. Open office applications sandboxed but I cannot find anywhere to buy it..just says it is free to use but page does not seem to have anywhere to pay 


from FAQ 

Office Suites (Libre Office, OpenOffice) (Support for MS Office 2016/Office365 is offered for the paid version)