Move your mouse until the white arrow is on top of the white square with "REPLY" written in it, then move your mouse to the big box next to "Message:" and click inside of it. Now look at your keyboard and hold down the "CTRL" key (it's at the bottom left of the keyboard) and then press the "V" key while still holding onto the CTRL key - don't forget this bit, it's very important. Now move your mouse until it's on top of the "Post" button and then click it.