From CSDS, select 'Music | Edit Music Database'; Then select 'Edit | Add New MP3 Files from Folder'; Enter the folder pathname, C:\SQDATA\MP3, and press OK. CSDS will then add the music to the music database.
If you name your music files of the form <title>-<label>-<number>.mp3, CSDS can extract the title, label, and record number and automatically populate the appropriate database fields. (e.g., 'TruckDrivingMan-Snow-202.mp3')
You should also edit your settings to tell CSDS where to look for music files. I.e., From the main menu, Select 'System | Settings...'; then select the 'Folders' tab; Edit field 'Music files' to say 'C:\SQDATA\MP3'. You also might want to create appropriate folders and set the 'Cue Sheet files' and 'Lyrics files' fields.