Open your history folder Firefox > History > Show All or <Shift + Control> H. Find the entry you want and click it once. The information boxes at the bottom of the window is where you can make changes or copy the information.

The long way around appears to be:

• long press the entry
• tap Share
• tap application to receive the URL
• in the receiving application, select and copy the URL

Or if you were planning to text/mail it off to someone anyway, that last step isn't needed.