To prepare yourselves for the first spreadsheet session, glance over ...
- About.com for some basic terminology you will be using
- Excel 2013 Courses and see if any are ones you need to view. You might want to bookmark all or parts of all of them.
- Part I: Worksheet Basics and Part II: Formulas and Functions in Excel 2013: The Missing Manual
These from About.com can also be useful
- About.com Formulas & Functions
- Excel 2007+ Formulas Step by Step Tutorial
- Using Excel Functions in Spreadsheets
As can these from Microsoft
- Entering a formula in Excel 2007+
- Excel Function reference
- you won't be asked to do it, but it might be useful to know that you can Create Custom Functions