Here's how to view your message threads on your Apple Watch:
Open the 2ndLine app on your Apple Watch. The app icon should be on your app list.
You'll see a list of your recent message threads. Each thread will typically display the sender's name or number, a snippet of the latest message, and potentially an unread message indicator.
To view a specific conversation: Tap on the desired message thread from the list. This will open the conversation history, allowing you to see all the messages exchanged in that thread.
Additional Tips:
If you have many messages, you might need to scroll up or down on the watch screen to see all conversations.