Go to your task bar at the top of your browser and cut the text out of the address bar when you have the page open that you want to link to.
Then got to thread that you want to post it in to.
Click on the little box that looks like a link from a chain above the black box that you write your text in.
Paste the text that you copied from the address bar in to the top section.
Write in to the bottom section the text of how you would like it to appear.
Its very easy once you have done it the first time
PS, If you still have trouble doing it let me know and I will video myself doing it and post that up.