That first and foremost currently depends on which program ((la)tex based, openoffice, libreoffice, microsoft word, … etc.) and also which citationstyle (MLA, APA, IEEE, … etc.) you use or would like to use to write your text.
- For the instance you use a tex based system and also use biblatex to manage the citationstyle, then this currently cannot be configured in Jabref, but is rather done in your tex document. Check out Biblatex documentation page 74 for some standart styles: https://mirror.physik.tu-berlin.de/pub/CTAN/macros/latex/contrib/biblatex/doc/biblatex.pdf
The following are examples of how you could put it into your preamble. Choose one of them or adapt to make your own. Most of them should include the URL, but i have not tried all of them. I know for a fact that the authoryear style includes the URL. If you want to turn the URL into a link, you can use the hyperref package.