To find this message again, click Other at the top of your list of Messages. Select Archived from the drop-down menu.
Select a conversation from the main Messages screen. Click the Actions icon at the top of the screen. This looks like a cogwheel. Select Delete Messages. . . from the drop-down menu. Click the checkbox next to each message you wish to delete. Click Delete in the lower right, then Delete Message in the pop-up confirmation window. To delete an entire conversation, select Delete Conversation from the Actions menu instead.
Tap the Messages icon (a pair of speech bubbles). Swipe left on the conversation you want to hide. Tap Archive.
Log onto Facebook. Open a conversation. Select Choose an action. Select Archive. Select Apply.
Tap the speech bubble icon. Press and hold the conversation you want to hide. Tap Archive.
Open your Facebook app. Tap the Messenger icon at the bottom of your screen. This looks like a lightning bolt. Swipe left on the conversation you’d like to hide. Tap More. Tap Archive.