Sage--use spkg coxeter3 in Sage notebook I want to use the well-known coxeter3  package (http://math.univ-lyon1.fr/~ducloux/coxeter/coxeter3/english/coxeter3_e.html) in sage-notebook. I've tried 'i' and 'f' but doesn't work, so far I couldn't find a 'good' answer online.
How to install the package so that I can use it in sage-notebook?
 A: If you installed Sage from source or from a binary
for Linux or macOS, you should be able to install
the coxeter3 package by opening a terminal and running
sage -i coxeter3

(type sage -i coxeter3 and hit the RETURN or ENTER key).
Providing you have the necessary development tools
available, this will install the package for your
version of Sage, and next time you start either the
Sage REPL (read-eval-print loop, or command-line interface
in the terminal), or the SageNB notebook, or the Jupyter
notebook with the SageMath kernel, you will be able to
use the functionality of the coxeter3 package.
This also assumes that your shell is configured so that
when you type sage in a terminal, this launches Sage.
If this is not the case, you need to open a terminal and
run something like
sudo ln -sf /path/to/sagedir/sage /usr/local/bin

where /path/to/sagedir should be replaced by the path to
the Sage directory (and you might need to type in your user
password for your user account on that Mac). If you don't
know what the path is to the Sage directory, you can obtain
it by launching Sage and running, in Sage,
print SAGE_ROOT

