Download and extract the latest release. Then, re-read what's in there if it's different than the following:
To install, just execute ./install.sh. If you wish to install psgrep
somewhere other than /usr/local/bin, set the $PREFIX variable like so:
PREFIX=/usr sudo ./install.sh
The default $PREFIX is /usr/local
If you, for example, install psgrep to your home directory, don't forget to set
your PATH to include ~/bin as well as your MANPATH (or ~/.manpath) to include
~/share/man.
For usage information, run
man psgrep