If you were using FrostWire v.4, you would be nagged to update everytime you opened the program. Also after downloading & installing FW 6 it appears to look quite noticeably different to version 4 which was both a basic torrent program but was primarily a gnutella network program.

FrostWire 4: . FrostWire 6:

If your previous version did not look like FW 4 then you were either using FW 5 or an earlier FW 6 version.

I still believe it is best for you to contact the developer to help solve your problem. There used to be a support chat channel but last time I searched for links to it, it had disappeared. You might be able to find the support channel under the FW Help menu or Community Support link. I also still suspect the problem is as I suggested previously, the new version has set everything back to default and you have lost custom settings including download & share folders. If you cannot remember what these folders were, then go to the FW App Data folder and open the various settings files. Some of these settings might still exist but are not properly linked.

Edited: Fixed the FW 6 image.