IF YOUR DATA FILE IS SMALL:
Whatever format your data are in, get data into CSV and then use Concatenate-text adaptor to add a header. Left argument is the header with commas and ends with a newline.

IF YOUR FILE IS LARGE:
Use Datatable-columns to turn the header row (which is really supposed to be your first row of data) into a list, Then use List-to-datatable so the list becomes the data in a new datatable column, then use Add-column to create a dummy column (for use in Spread-rows), then use Spread-rows to turn the column of column names into the values in a single row, then use Remove-column to get rid of the dummy column. Now your first row of data is both the header and the first row of data. Finally, use Merge-datatables with this as 'first data' and the original datatable (which has the first data-row as column names instead of as data) as 'second data'. Now you can Rename-columns and have all your data as data.

To see this example, make a copy of this Data-flo so you can see how it is built.