Are you attempting to create a surround Room?

AMP could be used for the rear surround 3rd party speakers.

Yes. Arc is at the front, SUB as an enhancement, AMP with two ceiling speakers as rear ones.

How can I connect them?

1. In the Sonos app, under the Arc’s settings, run “TV Setup” and follow the app instructions.

2. Then select “Connect Sub” under the Arc’s settings to bond the Sub to the Arc. Follow the app instructions.

3. Select “Set Up Surrounds” under the Arc’s settings to bond the Amp to the Arc. Follow the app instructions.

It may help to refer to the setting up Amp or CONNECT:AMP as surround speakers FAQ, although @GuitarSuperstar ‘s instructions cover it fairly well.