add HowToInstall to README; add folder internal

README.md

@@ -13,3 +13,18 @@ This is done in several steps:
   - provides that credentials to [matrix-synapse-rest-auth](https://github.com/kamax-io/matrix-synapse-rest-auth#integrate) which has to be configured to query login.php
 
 2nd step: Implement the other apis to integrade [mxisd](https://github.com/kamax-io/mxisd/blob/master/docs/backends/rest.md)
+
+## How to install
+
+- Copy `config.sample.php` to `config.php` and configure the bot as you can find there
+- Configure your webserver to publish the folder `public` and configure.
+  The folder `internal` contains files that can be accessed by mxisd or matrix-synapse-rest-auth
+- To integrate with matrix-synapse-rest-auth:
+  - `/_matrix-internal/identity/v1/check_credentials` should map to `internal/login.php`
+- To integrate with mxisd: Have a look at [the docs](https://github.com/kamax-io/mxisd/blob/master/docs/backends/rest.md) and apply as follows:
+| Key                            | file which handles that | Description                                          |
+|--------------------------------|-------------------------|------------------------------------------------------|
+| rest.endpoints.auth            | internal/login.php      | Validate credentials and get user profile            |
+| rest.endpoints.directory       | to follow               | Search for users by arbitrary input                  |
+| rest.endpoints.identity.single | to follow               | Endpoint to query a single 3PID                      |
+| rest.endpoints.identity.bulk   | to follow               | Endpoint to query a list of 3PID                     |