The Set Variable task can set a variable's value to static text, user-defined variables, data from a RowSet, or the contents of a file. When setting the value of a variable, either the Value or Input File attribute must be specified.
When using a RowSet variable, the Set Variable task must be inside a For Each Loop. For example, specifying a Value of ${data[1]} inside a loop will set your Variable Name to the value of the current row's first column.