Hi
The following documentation also will help you
https://docs.mendix.com/howto/data-models/working-with-images-and-files
Please see the documentation regarding FileDocument entity in Mendix that supports the uploading and downloading of files
https://docs.mendix.com/studio-how-to/pages-how-to-attach-files
https://docs.mendix.com/refguide/creating-your-own-documents
And if you want to import data from excel files then use the Excel Importer module