Two of the more active posters in the calibre forum are Kovid Goyal (kovidgoyal), the creator of calibre and Charles Haley (chaley) who is very actively involved in calibre's development. You can ask your questions in either the calibre forum or the appropriate subforum.
I would suggest browsing/searching through the calibre forum and subforums to see if your questions have already been asked and answered before posting any questions.
For instance, see
Are old manuals available ? for your question.