If you're worried about someone accessing your Facebook account from a different iPhone, iPad, or computer browser, you can enable a few security settings to set your mind at ease. Code Generator can give you access codes right on your iPhone and iPad so you can approve different devices and browsers as you see fit.
Before continuing, you'll need to make sure that Login Approvals are turned On for your Facebook account. You'll most likely need to do this via a desktop computer or the full version of the site via Safari on your iPhone or iPad. You can find Login Approvals under the Security Settings section of Facebook.
After you've done that, continue on.
That's all there is to it. Code Generator is great for times you may not have cell service but can access WiFi from one of your already authorized devices. Facebook will always send you a text authorization code to whatever cell phone number you have on file but if for some reason you can't access it, Code Generator will do the trick too.