git clone https://github.com/Neilpang/acme.sh.git
cd acme.sh
./acme.sh --install
Optionally, set the home dir and/or account info (if already have one).
If was previously using LetsEncrypt's certbot, can probably get account info from
/etc/letsencrypt/accounts/acme-v01.api.letsencrypt.org/directory/*/regr.json
.