From your description, it's not absolutely clear what you're doing, so I've had to make some assumptions with what follows.
The My Libraries folder in Stardraw AV's Library List can list user-generated symbol files in .S01 format only. The Library List does not support other file formats.
To add symbols to My Libraries that are based on another file format, e.g. .DWG, select File | Open to open the file, select the parts that you want to be your new symbol and drag into the Library List under My Libraries.
Note you can rightclick on folders under My Libraries to create a folder, rename, delete etc.
I hope this is helpful.