How do I click once to select all in firefox url

I don't know a real answer for your question but you can try to use CTRL + A on your keyboard to select all.

 I want it to be like internet explorer where all I have to do is to click on the url to select all

Do you mean you want to select whole the URL-box?
Then you have to click into the white ore yellow empty space behind the URL (if there is any space left).
When the URL is to long I don't know an answer to your question.

I use one of two methods:
- double click on the URL in the address bar and it will select the whole URL OR
- control + L will place the cursor in the location (or address) bar and select the entire URL.

ctrl+L

This question seems to be resolved in another way as wanted by Grig !

Nevertheless it takes no less time to do ctrl-L as to click once in the adress bar.

But I personally prefer a single mouse click too !
Furthermore, if you select the URL , it is to copy it.
for which you need to right click on the the mouse anyway !

Until now I was positioning the pointer at the end of the url and then "select" by shifting mouse and holding the left button down. Not the easiest way !