How to install the certificate:
1、直接点击安装
2、打开系统设置-安全与隐私-（更多安全设置）-凭据存储-从手机存储安装-CA证书
PS: Some mobile phones need to set the lock screen password first to install the certificate.
The installation prompts " Certificate file not found ", .pemchange the suffix certificate to .crtor .cersuffix and try again~