ValhallaRoom is a plugin. If you are running a very old, 32-bit version of a DAW (like really old Cubase 5), it will not load. You need a 64-bit DAW for the modern VST3 link.
ValhallaRoom is a commercial product.
The official way to obtain ValhallaRoom is directly from the developer's website. ValhallaRoom at Valhalla DSP Download/Installers Link: Valhalla DSP Demos & Downloads vst plugin valhallaroom vst3 link
: A free demo version is available on the same page for testing before purchase. ValhallaRoom is a plugin
This paper provides a guide to the ValhallaRoom reverb plugin, including its core features, installation process, and how to access the official VST3 installer. Overview of ValhallaRoom ValhallaRoom including its core features