I have an iPad mini and it is really very simple. Just tap on the "post Reply" button and it will bring up a box saying "choose file" tap on this and you will get a choice of "take photo" or "choose existing" the latter will take you your photos, then just tap on the one you want.
To post a link go to the address bar at the top of the selected page. Tap and hold on this until you get a option to "select all", tap this and then you an option to "cut", tap this. The link is then transferred to your "clipboard". Go to the post you are writing leave a space , put your finger on the screen, then release it. You then will get an option to "paste", select that and your link will appear.