You can find an excellent calculator guide for the Casio FX991EX-ClassWiz on Dr Frost’s site.
From Pearson-Edexcel, one of their excellent guides from the Teaching and Learning Materials collection, we have this guide to using calculators when teaching AS and A level Mathematics. This very clear 5 page document lists specification content for AS and A Level Mathematics and provides video tutorials for a Scientific Calculator (Casio ClassWiz) and a Graphics Calculator (Casio CG50).
Calculator Guide Classwiz resources.
Also from The Calculator Guide on YouTube see this comprehensive playlist on the Casio Classwiz fx-99EX. For example see this introductory video on using Statistics mode to find the mean, variance and other statistical summary data.
David Smith – Playlist for Classwiz – including Binomial Distribution and Normal Distribution.
See also this playlist from Casio on the Classwiz FX 991EX.
All Casio manuals and other resources can be found on the Casio website here.