l deleted a tile by mistake

[WPCentral Question]

how to get the tile back

 

[Harrie-S]

Go to the app list (swipe to the left on your start screen)
Tap and Hold the App and a dropdown menu will come with "pin to start"

 

[Zachary Boddy]

You have to be more specific, sir (or ma'am).
If you speak of Windows Phone 8.1, go to your All Apps list, find the app you wish to add to your Start Screen, press your finger to it and hold down until a menu comes up. Hit "Pin to Start" and the app will now be pinned, as a Live Tile, to the Start Screen. If you hold down on this Live Tile you can resize it with the arrow in the bottom right or remove it with the unpin button in the top right. You can also move it around by dragging.
If it's Windows 8.1, click the arrow pointing down on the Start Screen to take you to All Apps. Find the app, right click on it, and hit "Pin to Start." It'll now be pinned to your Start Screen. You can resize it, among other options, by right clicking on the tile. You can move it around by holding left click on it and dragging it to the appropriate spot.
Windows 10 (Mobile and desktop) work on the same premise.