Download the Excel Services Step by Step Guides from the following URL: http://technet.microsoft.com/en-us/library/cc263430.aspx

Following guides are available for your reading pleasure.

Setting up the Server - Step 1: Creating a Trusted Location with Excel Services

Setting up the Server - Step 2: Configuring Single Sign-On for Excel Services

Setting up the Server - Step 3: Creating a Trusted Data Connection Library with Excel Services

Building a Report Based on Cube Functions for Excel Web Access

Protecting Workbook Intellectual Property (IP) with View Item Rights

Using OLAP Formulas, Conditional Formatting, and Charts

Building an OLAP PivotTable Report with Excel Services

Building a Relational PivotTable Report with Excel Services

Building a Report with a Chart for Excel Web Access Based on Cube Functions

Creating a Multi-Report Summary Page of Reseller Sales Data

See this demo to learn how to enable Excel services and data connections for a SharePoint team site.