1) Find the page you want to link to
2) click on the address bar, it should highlight it, if it doesn't click on a blank part of the page heading then click again.
3)Hover over the highlighted bit and right click and select copy.
4) go to the area where you want the link to appear, eg the answer box in AB and press CTRL+V together or right click and select paste.
the above instructions make it look more involved than it is but it's really very simple.
If you're going to use CTRL + V to paste, then you may as well go the whole hog and use CTRL + C to copy - for desktop/laptops (most cases) only, I might add.
Personally I use CTRL + x, that way I know I've definitely managed to grab said link, or text (CTRL + X means to cut), as it disappears into the clipboard, ready to be pasted.