Well, I looked up how to copy the url. I did a long press and it did say "copy". Now how do I copy it to here?
Sorry, I didn't realize you're not familiar with copying and pasting.
Generally speaking, once you copy something it stays in your clipboard until you replace it with something else. How you get it there depends on the OS you're using and/or what kind of device it's on.
On Linux and its offspring, Android, you can copy by selecting the text you want, then pressing [ctrl][c] on your keyboard. Note that not all Android keyboards have a [ctrl] key; mine does:
On computers, you can highlight text by using its trackball/mouse; just left-click on the text and scroll over while still clicking. Once it's highlighted, copy it by pressing [ctrl][c] or by right-clicking and choosing 'copy.'
On Android devices, press on any part of the desired text, then use the left/right controls that appear and highlight everything you want. Then use either [ctrl][c] or press 'copy' in the menu that appears.
Once it's in your clipboard, paste it where you want by pressing [ctrl][v], or by choosing 'paste' in the menu that should appear when you're somewhere that accepts text--like here. Say you're writing a reply; you've copied something, like a URL. In your reply, where you want the URL to appear, just put your cursor there and paste as above.
There are other things related to copying/pasting, but they're irrelevant right now. And, of course, I don't do window$ or Mac, only Linux, so someone else will have to help if you need it with those.