Step1: In a channel conversation, in the message compose box, press Shift+Tab to go to the last message in the channel.
Step2: Press the Up or Down arrow key until you hear the first message in the conversation you want to enable notifications for.
Step3: Press Enter. You hear: “Like.” You may need to press Enter twice.
Step4: Press the Tab key once. You hear: “More options.” Press Enter to select.
Step5: Press the Down arrow key until you hear “Turn on notifications,” and then press Enter to select.
Step6: If you hear a confirmation dialog box prompt, press Spacebar to confirm and apply the change.
Step7: To return the focus to the message, press Esc.