Step 1
Download the appropriate .qpkg file from below the page. Open "App Center" and click either the icon "Install Manually" (see screenshot) or the gear icon to get "Install Manually" option (depends on version).
Step 2
Click "Browse..." to select the downloaded package. After selecting the .qpkg you downloaded for your NAS (download links below) click "Install".
If the appropriate package has been chosen, but you still get the warning:
that may occur if the package certificate validation failed and can be bypassed via the "Settings > General" of the Application Center:
Version and usage compatibility
If you use Resilio Sync for personal non-commercial usage, you can update to and install Resilio Sync v3If you use Resilio Sync Business, please continue using Resilio Sync v2. The latest available version is 2.8.1.
Important warning: DO NOT attempt to update your current Resilio Sync Business installation to Resilio Sync v3, it is not supported and access to the configured shares will be lost. Reinstalling of Sync will be required. Resilio Sync Business needs to stay on v2.
Resilio Sync v3 is supported only for personal usage. For commercial business use, please download Resilio Sync v2.
If you use Resilio Sync Business, please install Sync v2.
If you have a QNAP device with ARM, you are most likely to use the x19 or x09 package unless you know you have an x31.
If you have a QNAP device with x86, you are most likely to use the x86 package before x86_64.
x09 series (ARM)
x19 series (ARM)
x31 series (ARM)
x41 series (ARM)
arm64
ce53xx series
x86_64
x86