I will describe the execution procedure in my CentOS environment.
$ wget https://artifacts.elastic.co/downloads/enterprise-search/enterprise-search-7.12.1.rpm
$ rpm -ivh enterprise-search-7.12.1
$ cd /usr/share/enterprise-search/
$ vi config/enterprise-search.yml
... snip ...
$ systemctl start enterprise-search
$ ENT_SEARCH_DEFAULT_PASSWORD=[REDACTED] bin/enterprise-search&