Outlook 2016

[ck1]

I've just had to reinstall Office 2016 and can't seem to access the existing ost file. Is there a way to import this?

[Buenchico]

The Microsoft website says that you can't manually import a .ost file but then goes on to explain about recreating one. I have to admit that I don't fully understand the difference but I'll offer you the link anyway:
https://support.office.com/en-ie/article/open-or-import-items-from-an-offline-outlook-data-file-ost-a584963e-a66d-4d9d-8845-31cb270f6880

If that's no use there are several commercial software programs which claim that they can import .ost files but I know nothing about any of them, so I'm not going to recommend a particular one. (Google 'import.ost' to look for possible solutions but be aware that they tend not to be cheap. One I've just looked at costs £64.95)