Edit excel template in sharepoint online document library

Hi! 

(My first post in this forum so maybe this question has been answered 1000 times already, but I've tried googeling on forehand). 

So I've uploaded an excel template to my Sharepoint online document library but I can't figure out how to edit the template file. I was able to find how to edit the "word-template-file" but not to change which file to be edited. 

Any ideas?