Putting 365 on new PC. Old machine gone to it's grave.

Hi everybody
My wife machine died on her and I have had to get a new PC (arriving tomorrow) She is a translator and does lots of work for Microsoft through translation houses. She was translating a project to be completed by Monday and then bang into another project, so as you might agree, she can't afford to be down. Windows 10 Home 64 will already be installed.
However I have to get everything back to normal for her by tomorrow night. Fortunately she keeps her back ups externally so no issue there. Likewise with translation tools etc.
This might sound silly, but I need to get her new machine loaded with 365 which we have a multiple licence. My problem is that I think we are already using up 5 machines including her old one.
So my question is, how do I get 365 onto her new machine?
Many thanks to anybody who can help me.