After you create your cert + cert key, enable by updating nginx
sudo gitlab-ctl hup nginx
# in /etc/gitlab/gitlab.rb
nginx['ssl_certificate'] = "/etc/gitlab/ssl/#{node['fqdn']}.crt"
nginx['ssl_certificate_key'] = "/etc/gitlab/ssl/#{node['fqdn']}.key"
then reconfigure gitlab:
sudo gitlab-ctl reconfigure
# UFW example (Debian, Ubuntu)
sudo ufw allow https
# lokkit example (RedHat, CentOS 6)
sudo lokkit -s https
# firewall-cmd (RedHat, Centos 7)
sudo firewall-cmd --permanent --add-service=https
sudo systemctl reload firewalld