Open the download options
Select Open download page to reach the external service. Look for its Android, iPhone or browser option. The link does not itself identify an APK, and this page has no verified package size, version or minimum Android requirement. Read those details on the download screen before choosing a file.
Install a downloaded Android file
If you chose an Android package, wait for the transfer to finish, open Downloads on the phone and select that file. Follow the device prompts. If installation is blocked, read the warning before changing anything; do not turn off device protection to force an unknown file to run.
Already installed?
Open the existing app and use the account you registered previously. An app update is not a reason to create another account. If the downloaded file will not install, note the error and check available storage and the published device requirement before downloading again.