See here.
Participants should install the coq-metacoq-template package via opam.
If you do not have Coq installed yet, we recommend using the Coq platform to install.
If you do not already have an editor for Coq installed, we recommend using VSCode with the VSCoq legacy plugin.
See also MetaCoq's installation instructions. If you have trouble installing, you can ask questions on MetaCoq's Zulip channel.