Hello @Charlie20,
Welcome to the Knime Forum.
Creating a column sum is quite easy in BIRT.
First create your output in the KNIME workflow. Then use the
node to export the data to BIRT.
Now open BIRT (using the diagram button). Then create a table in your BIRT report and bind it to your data.
The table in BIRT has a footer. Here you can select a column in the footer and put dynamic data in here. In the bindings for the data you can select for example the sum over the table.