add some docs

Author: markns

README.md

@@ -1,5 +1,42 @@
-# Excel client for Materialize using ExcelDNA
+# Excel client for Materialize using System.Reactive and Excel-DNA
 
+[Materialize](https://materialize.com/) is an awesome streaming SQL database. 
+
+Excel is... better at displaying real-time data than many people realize.
+
+This add-in provides a single UDF `=MZ_TAIL(query)` where query is an object (source, table, view) name or select statement.
+
+![MZ_TAIL usage](doc/mz_tail.gif?raw=true "MZ_TAIL")
+
+There is also a custom task pane which displays the data catalog from the Materialize server.
+
+![custom task page](doc/mz_task_pane.gif?raw=true "Custom task pane")
+
+## Installation
+
+Download the release or build the solution yourself (artifacts will be in `MaterializeExcel.AddIn\bin\Debug`).
+
+Edit the `.config` file for your Materialize host.
+```
+<MaterializeExcel.AddIn.Properties.Settings>
+    <setting name="Host" serializeAs="String">
+        <value>localhost</value>
+    </setting>
+    <setting name="Port" serializeAs="String">
+        <value>6875</value>
+    </setting>
+    <setting name="Database" serializeAs="String">
+        <value>materialize</value>
+    </setting>
+    <setting name="User" serializeAs="String">
+        <value>materialize</value>
+    </setting>
+</MaterializeExcel.AddIn.Properties.Settings>
+```
+
+Follow the [Add or remove an Excel add-in](https://support.microsoft.com/en-us/office/add-or-remove-add-ins-in-excel-0af570c4-5cf3-4fa9-9b88-403625a0b460) instructions from Microsoft. Make sure the `.xll` and `.config` files stay together. 
+
+Note - Excel will complain about this being an unsigned/untrusted add-in. Read and build the code yourself if you prefer.  
 
 ## Materialize demo set up
 
@@ -13,4 +50,6 @@ Only works with native Excel 365 on Windows.
 
 Order by clauses are not implemented.
 
-Large grids are currently inefficient due to copy from multiset to 2d array.
+Large grids are currently inefficient due to copy from multiset to 2d array.
+
+Only simple username login is implemented.