The VelongVPN iOS app is not available on Chinese AppleID accounts. If you have a Chinese AppleID, you will not be able to download the VelongVPN/OpenVPN connect app. If you use a Android phone, you can download the APK for the app directly.
After downloading the app, you should see an import profile page which prompts you for a URL. Enter velong.duck.enterprises as the url, and press next. If anything pops up press accept. You should now see a sign in page, enter your username and password.
IMPORTANT: Make sure to check "Import Autologin Profile" before importing.