expression, ichidan verb
tune in to a channel; switch to a channel
Used for selecting a TV or radio channel, either by turning a dial or pressing a button.
リモコンでチャンネルを合わせる。
I change the channel with the remote control.
このラジオは、ダイヤルを回してチャンネルを合わせます。
You tune this radio by turning the dial.
More general 'change the channel'; 合わせる implies tuning or selecting a specific channel, often with a dial or precise action.
Phrase combining チャンネル (channel) and 合わせる (to match, to tune).