I need to link my apple tv remote to my bose sound

If your sound system had an IR signal receiver, then the Siri remote would be able to use that. Set Apple TV to work that way: Settings﹥Remotes and Devices﹥Volume Control﹥Receiver via IR.

If the standard volume control IR signals are not recognized by your sound system, then you may learn the remote a new device: Settings﹥Remotes and Devices﹥Volume Control﹥Learn New Device. Then follow the on-screen instructions.

If your sound system uses bluetooth or some other proprietary protocol for remotes, then the Apple TV remote isn’t usable for that.

If your sound system supports HDMI-CEC for Volume Control (optional CEC functionality), then the volume may be controlled through the Apple TV box and its remote. Settings﹥Remotes and Devices﹥Volume Control﹥Auto via HDMI (receiver).