This is straightforward and you don't need to create a wiki if you're looking for students to access the file as is from the course outline.
To do this you should 'display a directory'. Here's how:
- Go to the Files area of your course (in Administration block)
- Create a new directory. It doesn't matter what it's called, but you might want to call it 'excel documents'
- click on it to enter the directory.
- Now you want to browse and upload the Excel document that you want to make available.
- Having done this, return to the main course outline and make sure that Editing is switched on.
- Find the weekly or topic block that you want to present the file in and choose Add a resource -> Display a directory
- Give the resource a name, perhaps, 'Excel files' and in the summary say what kind of spreadsheets are going here. Pull down Display a directory and choose the 'Excel documents' directory. Click Save changes.
- Now the contents of this directory will be displayed to your students when they click the resource link.