Improve readme

Author: pont-us

README.md

@@ -1,3 +1,57 @@
 # xarray-enmap
 
-An xarray backend to read EnMAP archives.
+An xarray backend to read the data archives provided by the EOWEB data portal
+of the [EnMAP](https://www.enmap.org/) mission.
+
+## Installation
+
+### With mamba or conda
+
+`mamba install xarray-enmap`
+
+or
+
+`conda install xarray-enmap`
+
+### With pip
+
+`pip install xarray-enmap`
+
+### Development install from the git repository
+
+Clone the repository and set the current working directory:
+
+```bash
+git clone https://github.com/bcdev/xarray-enmap.git
+cd xarray-enmap
+```
+
+Install the dependencies with mamba or conda:
+
+```bash
+mamba env create
+mamba activate xarray-enmap
+```
+
+Install xarray-enmap itself:
+
+```bash
+pip install --no-deps editable .
+```
+
+## Usage
+
+```
+import xarray as xr
+
+enmap_dataset = xr.open_dataset(
+    "/path/to/enmap/data/filename.tar.gz",
+    engine="enmap"
+)
+```
+
+The path can be to either a `.tar.gz` archive as provided by the EnMAP portal,
+or to a directory containing the extracted archive contents.
+
+If the archive or directory contains multiple EnMAP products, xarray-enmap
+will open only the first. This will be improved in a future version.