Sharing data between steps can be somewhat confusing when writing your first formula.  All steps make data available to other steps by exposing variables with the results of executing the step.  For most step types, this is specific to the particular type. The one exception to this is the script step which exposes the contents of the Javascript object that the step passes into the done function.

There are two different ways of referencing these step variables, depending on where you're trying to use them.  If you're referencing them from Javascript (in a script or filter step), you refer to them via the steps variable available to your Javascript that contains the most recent results of every step execution.  For example, steps.myStepName.myVariableName.

However, when referencing a variable from within the configuration for a step, you need to surround the reference with ${}.  For example, ${steps.myStepName.myVariableName}