Welcome to Android Central! Which phone? Do you mean you removed a homescreen shortcut for the Settings menu? Open your App Drawer, find the Settings icon there, long-press it, and drag-and-drop it back to the homescreen. (You can also access it by swiping down the notification panel twice and looking for the gear icon there.)
For your Messages app, do the same -- find it in your App Drawer and drag-and-drop it back to the homescreen.
Go into your settings from your pulldown status bar. There should be a gear icon when you pull down your status bar. From there, go into your apps and see if those two apps are disabled.