The primary source for Stool is its GitHub page (maintained by the original developer or a community fork). Look for the "Releases" tag. The file name typically follows stool-1.64.tar.gz (source code) or a precompiled binary for Linux x86_64.
For a stable installation and operation, follow these steps: the STool_MTool_v1.64.7z file. Unzip the contents into a dedicated folder on your desktop. Stool 1.64 Download