上網站填寫資料
https://www.sslforfree.com/
(注意:這種做法有資安疑慮)

都填完後會有一個下載壓縮檔給你 sslforfree.zip

解壓縮後丟到某個目錄去即可 例如像是
/etc/letsencrypt/live/sslforfree
壓縮檔裡面應該會有 private.key certificate.crt ca_bundle.crt三個檔案

你的apache的ssl.conf (/etc/httpd/conf.d/ssl.conf)裡面加上
SSLCertificateFile /etc/letsencrypt/live/sslforfree/certificate.crt
SSLCertificateKeyFile /etc/letsencrypt/live/sslforfree/private.key

# Certificate Authority (CA):
SSLCACertificateFile /etc/letsencrypt/live/sslforfree/ca_bundle.crt
這幾行後
#service httpd restart
即可