can I lock messages which I don't want someone should see
I think we're going to need more information about your issue before anyone can help.
What messages are you referring to? Are you wanting to keep Messages in the Apple messaging application locked? If so, the only way I know of to do that is to be sure your entire device is locked with a secure password and/or TouchID. 1Password can't help with that. You would also need to turn off notifications on the lock screen to prevent those from appearing as messages arrive.
But if you have something else in mind, post back and someone will try to help.
@Sheikh: Assuming I'm understanding your question (correct me if I'm wrong), it sounds like you're trying to lock/secure/encrypt messages (text/iMessage?) using 1Password. This is not possible.
Now, you could copy the text of a message, paste it into a Secure Note in 1Password, and then delete the original. And while 1Password would not be able to ensure that the original is securely deleted, any information you store in your 1Password vault is secured using your Master Password.
Just be aware that iOS itself does not let apps access each other's data, so there isn't any way from 1Password to 'reach' into Messages, for example, and lock something there. I hope this helps. Be sure to let us know if you have any other questions!