update readme

README.md

@@ -1,3 +1,25 @@
 # GatewayAPIKit
 
-A description of this package.
+### GatewayAPIKit is a Swift package used to send text messages (SMS) with [GatewayAPI](https://gatewayapi.com/) for Server Side Swift.
+
+## Installation
+To use GatewayAPI, please add the following to your `Package.swift` file.
+
+~~~~swift
+.package(url: "https://github.com/madsodgaard/GatewayAPIKit.git", from: "0.1.0")
+~~~~
+
+## How to use
+All you need to send a text message is to initialize a `GatewayAPIClient`:
+
+~~~~swift
+let elg = MultiThreadedEventLoopGroup(numberOfThreads: System.coreCount)
+let client = GatewayAPIClient(eventLoopGroup: elg, apiKey: "apikey")
+~~~~
+
+Please store your API key in storage such as environment variables and not directly in code.
+
+You can now send a simple text message:
+~~~~swift
+client.send("My text message", to: ["4510203040"], from: "Mads")
+~~~~