Please download the BitTorrent Client from here: https://www.bittorrent.com/products/win/bittorrent-classic-compare/
Follow the instructions on the installer.
If you get any errors during the installation process, feel free to submit a ticket including a screenshot: https://help.bittorrent.com/support/tickets/new
We will make sure to get back to you within 24-48 business hours.