HTC One M8 for Windows - Manual (Page 113)

Forwarding a message
1. In the threads list, tap a contact (or phone number) to display the
exchange of messages with that contact.
2. Press and hold the message you want to forward, and then tap
forward.
3. Fill in the recipient.
4. Tap to send.
Deleting a message
1. In the threads list, tap a contact (or phone number) to display the
exchange of messages with that contact.
2. Press and hold the message you want to delete, and then tap
delete.
Deleting a whole conversation
In the threads list, press and hold a contact (or phone number) whose
messages you want to delete, and then tap delete.
Messaging 113