Add README text

Author: SpeedJack

README.md

@@ -1,2 +1,32 @@
 # GridShow
 XenForo 2.x AddOn to show a grid of tiles in homepage.
+
+![gridshow](https://github.com/InforgeNet/GridShow/wiki/images/gridshow.png)
+
+## Installation
+
+Download the [latest
+release](https://github.com/InforgeNet/GridShow/releases/latest) and follow the
+instructions of [installing an add-on for
+XenForo2](https://xenforo.com/xf2-docs/manual/add-ons/)
+
+For development, fork the repository and then clone the fork in the
+`src/addon/Inforge/GridShow` directory of your development board.
+
+## Usage
+
+In the admin panel you will find the _GridShow_ menu. Here, you can add new
+tiles to display to your users. You can set as many tiles as you want but the
+add-on will display only the first 12.
+
+Users must have the `View tiles` permission set to view the tiles in homepage
+(default enabled). Admins must have the `Manage GridShow tiles` permission set
+to view the _GridShow_ menu in the admin panel.
+
+From `Appearence > Style properties > GridShow Widget` you can modify the style
+of the addon.
+
+### Help
+
+If you have a problem with this addon, open an
+[issue](https://github.com/InforgeNet/GridShow/issues/new).