Two introductory documents are available, one short and one longer:
The above links to PDF documents are to copies at eiffel.com. You can also find all PDF documents as part of the installation, in $ISE_EIFFEL/docs/PDF where $ISE_EIFFEL is the directory (folder) where you have installed ISE Eiffel.
Once you know the basics, it's always useful to take a look at the EiffelBase classes for examples and guidance. You will find them in the delivery at $ISE_EIFFEL/library/base where $ISE_EIFFEL is the directory (folder) where you have installed ISE Eiffel. You might start with the list classes at $ISE_EIFFEL/library/base/structures/list.
To become truly proficient in the method, read the book Object-Oriented Software Construction, 2nd edition; for a full description of the language, get the book Eiffel: The Language. (These two links require Web access.)
See the list of introductory documents covering not only the language but also the environment and general presentations of Eiffel.