To create a new Data Set in BIRT first make sure you have created a Data Source(database connection, flat file, etc)

In the Data Explorer right click Data Sets and choose “New Data Set”

In the New Data Set window select your Data Source and then name your data set in the “Data Set Name” box and click next.

If your report is a SQL query enter your query text.

Make sure your output columns types match your source data.

Preview you Data Set Results to make sure it is retrieving your data from the data source

BIRT Tutorial