  Fisher matrices are used frequently in the analysis of combining cosmological
constraints from various data sets. They encode the Gaussian uncertainties of
multiple variables. They are simple to use, and I show how to get up and
running with them quickly. Python software is also provided. I cover how to
obtain confidence ellipses, add datasets, apply priors, marginalize, transform
variables, and even calculate your own Fisher matrices. This treatment is not
new, but I aim to provide a clear and concise reference guide. I also provide
references and links to more sophisticated treatments and software.
