Okay, first go down to the quick reply box. Click on the picture I've circled here.
https://i52.tinypic.com/1yo191.png
Copy and paste the link you want into the box.
https://i53.tinypic.com/30t5nih.png
It'll then show you the link, and the link again highlighted.
https://i55.tinypic.com/2yzc1zt.png
You can replace this highlighted text (the text within the ] [ brackets) with whatever you want the "name" of your link to be.
https://i53.tinypic.com/fdha9g.png
When you post it, it'll show up like this! A clickable link with the "name" being whatever you want.
https://i53.tinypic.com/qmytk1.png
Hope I helped!