Make sure you select the BBCode first. Once that is selected, then choose the Original size (by choosing the Original size, you will keep the EXIF data intact).
After you paste the code, it should look like this:
PHP:
[url=https://flic.kr/p/qpFPHY][img]https://farm8.staticflickr.com/7514/16020611750_1cac2680d3_o.jpg[/img][/url][url=https://flic.kr/p/qpFPHY]Untitled[/url] by [url=https://www.flickr.com/people/128747886@N06/]petergillett12[/url], on Flickr
The next thing you want to do is to insert your cursor and hit ENTER once into the middle of the code. Even though this particular code looks like it is written on two different lines, you want to intentionally place your cursor AFTER the ] bracket--the bracket that follows the [/url]--and hit ENTER once. If you don't, you will wind up with Flickr's text off to the side of the photo instead of underneath it.