Here we begin our first tutorial in the [B/D] programming language, our computer implementation of the Bayes linear methodology. We begin by showing you how to start the program, and how to stop! Once we are underway, we introduce some simple, but basic concepts: the declaration of quantities and collections of quantities; the specification of covariances between quantities; and observations made on quantities. Throughout these early tutorial sessions we will try and keep our usage and description of the program as simple as possible - this is not the place to describe the much richer set of possibilies that the [B/D] language offers.