There are several documents available from the Support website which will describe the basics, the capabilities and the features of the Steelhead appliances.
The Management Console Users Guide, which describes the various parts of the GUI of the Steelhead appliance.
The Deployment Guide, which describes various deployment scenarios and integration issues.
The Hardware Maintenance Guide, which describes the steps for installing new hardware into a Steelhead appliance and replacing hardware into a Steelhead appliance received via an RMA.