ReductionEffect
The easiest way to install the latest released version of Reduction Effects is via OPAM:
opam repo add coq-released https://coq.inria.fr/opam/released
opam install coq-reduction-effects
To instead build and install manually, do:
git clone https://github.com/coq-community/reduction-effects.git
cd reduction-effects
make # or make -j <number-of-cores-on-your-machine>
make install