After downloading the entire Bitcoiin blockchain from a torrent, what are my next steps to link it to Bitcoin Core 0.17.1?
You should not use a torrent to download the blockchain.  There is no general purpose to using a torrent, as using it makes synchronization slower because validation (which is the slow part) cannot proceed concurrently with download.  Because there is no purpose to using a torrent, I wouldn't trust that any particular torrent wasn't made maliciously and didn't contain things that might be used to exploit your computer.