A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
If this is possible or not, resp. how depends on the kind of object.
I guess you have inserted a Word file into an Excel spreadsheet as described here
https://support.office.com/en-ie/article/insert...
And unfortunately it is not possible to rotate this kind of object.
The only way is to copy the object in Excel (right-click and copy) then right-click a cell and choose PasteSpecial... and paste a picture.
After that you can rotate the picture as mentioned by the other advisors.
I guess further you don't like that, so the only other way is to change the orientation of the spreadsheet, see screenshot below.
Andreas.