Add multiple data sources by clicking the "add data source..." button in the Data Source(s) section.
You should give each data source a unique name, e.g. "csat" for your customer satisfaction database. Tables and charts can point to a specific data source using its name. The first (default) data source doesn't need a name, because all tables and charts will point to it by default.
After selecting a table or chart in the project tree, look in the DATA tab for a button labeled "SRC". Click that button to change to data source for the selected table or chart.
A table or chart cannot point to more than one data source. So you won't be able to use multiple data sources feature to stack multiple waves. (pre-stack them in SPSS if you need to do that). The multiple data sources feature is useful when your report must point to datasets with different sets of variables (e.g., from different questionnaires), or multiple query results from a SQL database.