Look at the Tools/Options/File Location dialog. (This is based on standard view rather than Theater view.)
Under Audio, the first setting specifies the base folder where files are stored when you rip an audio CD. For example, you might specifiy F:\music\ if your external drive is drive F:.
The second setting specifies a rule for the folder where files are placed. The third setting specifies a rule for creating file names. The second and third settings can use data fields (tag values) in creating folder and file names.
Bill