You can customise the toggles by clicking the pencil icon in the top right. You should then be able to add a wifi toggle icon.

Edit: Ok. It seems like Verizon have removed that toggle. If you're rooted you can add it back though. See link [here][1] (contains screenshots).

> You need to download and install SQLite Editor - you need to download and install [SQLite Editor][2]

> 1. Open up SQLite Editor - Select the Apps tab on top and scroll down until you see Settings Storage and click it.
> 
> 2. Click on Settings.db
> 
> 3. Click on system
> 
> 4. Click on the search icon on top right
> 
> 5. Type in the word notification in the Filter Value field and click ok
> 
> 6. Once the results load up, tap on notification_panel_active_app_list (should be the bottom result) and click on the pencil icon on top to
> edit
> 
> 7. In the Value field, you'll see all your toggles listed. All you have to do is add the word Wifi <-- just like that with a semi colon
> right after. Make sure there's no space after the semi colon like in
> the screenshot below. Once you add Wifi, click the save button.
> 
> 8. Close SQLite editor and reboot your phone. Once your phone boots back up, you should now have the Wifi toggle in quick settings!


  [1]: http://www.droidforums.net/forum/android-news/245663-sgs4-hack-add-wifi-toggle-your-samsung-galaxy-s4.html
  [2]: https://play.google.com/store/apps/d...qleditor&hl=en