Focus, once installed, can be launched via command line or via the desktop files in Linux and .app files in macOS.
First, locate the installation directory. Assuming that Focus is installed in <focus_dir>, Focus can be launched via the executable file in the bin directory of the <focus_dir> as follows:
cd <focus_dir>
./bin/focus
The desktop files are automatically placed when installed from source and the Focus application can be launched using these files. Go to Applications and search for focus.
We build apps for macOS, and they can be launched via spotlight search for focus.