There are a few options for this, they are (definitions from Books Online):
• Append: Appends data to an existing file. The metadata of the appended data must match the file format.
• Create always: Always creates a new file.
• Create once: Creates a new file. If the file exists, the component fails.
• Truncate and append: Truncates an existing file and then writes the data to the file. The metadata of the appended data must match the file format.
Missing from this list is a Create First Time or Create Metadata option. As you begin to use the file format more, you’ll realize that this is an important option to have. Please, help out by voting for a metadata option for raw files.
At this point, you can move to the next screen and select the columns you need. There is a select all checkbox for SQL Server 2008 and forward, which is quite handy. For SQL Server 2005, you need to select all of the columns individually.