How do I access data in a file from a fileuploadfield

How do I access data in a file from a fileuploadfield

Follwowing situation
  1. I have a file upload field "myFile" in a custom module "myModule"
  2. The file is an xlsx
How can I access the data in this file (e.g. loop through each row and extract data).
I later want to write the data from the xlsx into a subform "myTable" of the same entry.

Thanks for any help!