Fix up docs

README.md

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+# silverstripe-xero
+
+## Maintainer Contact
+
+* Will Rossiter <[email protected]>
+
+## Installation
+
+> composer require "fullscreeninteractive/silverstripe-xero"
+
+## Documentation
+
+Provides a lightweight wrapper around `calcinai/xero-php` with additional
+Silverstripe support for authenication and connecting applications via oauth.
+
+To setup register a Xero Application and define your clientId and clientSecret
+as environment variables.
+
+```
+XERO_CLIENT_ID='123'
+XERO_CLIENT_SECRET='123'
+```
+
+Once those API keys are available, a new tab under the `Settings` admin will
+appear for connecting to Xero. Follow the prompts to link the selected account
+to your Silverstripe website.
+
+## Interacting with the API
+
+```
+/** @var \XeroPHP\Application **/
+$app = XeroFactory::singleton()->getApplication();
+```
+
+Integrating with the API is done via https://github.com/calcinai/xero-php.
+Consult that page for further information for creating invoices etc.
+