Do you mean the screen you get by pulling down the Status Bar with one finger? If so:
1. for the original version of the operating system, it's already there, but just not as a standard toggle. One can click on the notification and get to the toggle.
2. for the upgrade of the operating system, normally you have to reset the phone first and the toggle will be an available choice. If it is not one of the five displayed in the top part of the screen, one can scroll to the right to get to the location of the toggle.
3. after the upgrade and the reset, you can make that toggle one of the first five by choosing Edit mode once you get to the screen showing all the toggles (either using a two-finger pull-down or selecting the menu icon if the upper right).
Again, if this is what you mean, @vgjfelix has a video on how to do this in the Sticky section (it's the second one) and is video #1 in his post. But you would first need to get the upgrade and then reset the phone.
Yes I mean the pull down Status bar, the toggle is not listed for Wi-Fi . I watched the vide on how to move the toggles but I don't the Wi-Fi toggle. The Wi-Fi seems to be the only one I don't have.
He's talking a FDR, factory data reset, where you'll lose all data. Contacts and calendar should resynch from Google, and apps will reload (including some you deleted), and all of your other data will be gone. Kind of like having someone casually say "just reload windows". Unless you are prepared for having to somehow backup and recover your files, you'll have to ask yourself if a toggle is worth hours of recovering files, removing extra apps, and making all of your setting changes again. If you do want to do this, then search on S4 FDR.
It is simply baffling that Android does not have a built in backup and restore capability that would allow you to recover nearly everything after an FDR. I understand where they would not want absolutely everything restored since you may wind up restoring what caused the original problem. Still - that isn't an excuse to not only do nothing, but further provide no ability for non-root third-party apps to back everything up. I'm real surprised that ElGoog hasn't added a pay service to allow apps to sync their settings and files to Google. Seems to me there would be a number of ways to do this.
Also would be nice to have a semi-hard reset (don't go there) where system files are set back to factory but app files are retained.