In addition to the quickstart guide that comes with your KNIME installation you can find on these pages a collection of additional documentation that is available for KNIME.
Under KNIME you can find step by step explanations on how to install KNIME, how to get started by building a simple workflow, an introduction to the workbench, or for more advanced users, a description on how to use meta nodes.
The screencasts show you in short online movies how you can quickly get started with KNIME.
The reporting documentation describes how to create basic reports based on KNIME workflows. The screencasts show you can learn how to use variables within reports or how to include a chemical structure representation in your reports.