Open the Messages app
Select the conversation
Press and hold the message you want to delete
Tap Delete
Confirm deletion if prompted
To delete multiple messages, open the conversation
Tap More or Edit
Select the messages
Tap Delete
Confirm deletion if prompted
To delete an entire conversation, swipe left on the conversation
Tap Delete
Confirm deletion if prompted
On Android, open the Messages app
Press and hold the message or conversation
Tap Delete
Confirm deletion if prompted
To clear all messages, open the app settings if available
Use the delete or clear conversations option
Confirm deletion if prompted