Transmission is a free, open source, and cross platform bittorrent client. It's a stable and efficient client with minimal resource usage. Lacks alot of features that qBittorrent has but in turn can handle large quantities of torrents with ease. Great for mass seeding.
Go to Transmission's download page.
Download the installer for your operating system. You'll see two options for Windows, i.e,
transmission-4.0.3-x86.msi. Most likely you are on a
x64machine and should install that.
Run the installer and you're pretty much done.