while on the page you wish to link to ...click on the text in the adress bar so it is highlighted (blue) then with your cursor on the blue , right click and select copy.
now in the reply that you wish to link from click on the little earth in the second row of icons and a pair of [url] brackets will appear...put your cursor between them and right click...select paste and the link will appear between the brackets. when you post the link will be there and clickable