On the Casio website, you will find quick guides for Casio Calculators including the ClassWiz.
For the complete manual from Casio see this page, note the calculator is listed under fx-570EX / fx-911EX on the Casio manuals page.
From The Calculator Guide on YouTube see this playlist on the Casio Classwiz fx-991EX. For example see this introductory video on using Statistics mode to find the mean, variance and other statistical summary data.
For entering data from a frequency table:
For more features…
Other examples include further statistical videos such as Normal Distribution calculations, further Normal Distribution examples, integration and differential calculations and using Complex mode.
See also this playlist from Casio on the Classwiz FX 991EX.
Mathematics for Students 