Update README.md with package instructions (#19)

* Update README.md with package instructions
  - close #14 
  - list supported platforms

---------

Co-authored-by: Lily Wang <[email protected]>
Co-authored-by: Irfan Alibay <[email protected]>

README.md

@@ -1,4 +1,25 @@
 hole
 ====
 
-A program to analyze the pore dimensions of ion channels please see homepage: http://www.holeprogram.org/
+A program to analyze the pore dimensions of ion channels. 
+
+Please see the homepage http://www.holeprogram.org/ for further information.
+
+Supported platforms
+-------------------
+
+* Linux
+* macOS (experimental, Intel chips confirmed to work)
+
+Installation
+------------
+
+* **Source code** is available at https://github.com/osmart/hole2/ . Compiling requires a working FORTRAN compiler. See [INSTALL.md](INSTALL.md) for installation instructions.
+
+* For **Linux**, the [hole2 conda-forge package](https://anaconda.org/conda-forge/hole2) is available and can be installed with
+  ```bash
+  conda install -c conda-forge hole2
+  ```
+* For **macOS** with *Intel chips* (x86_64)  an _experimental_ conda-forge [hole2 package](https://anaconda.org/conda-forge/hole2) is also available. The newer **ARM64 (M1/M2) chips are currently not supported** as a conda-forge package, see issue [#3](https://github.com/osmart/hole2/issues/3).
+
+* For **Windows** you need to compile `hole2` yourself but this has never been officially supported. If you succeed in building hole2 in Windows then please share successful recipes in issue [#16](https://github.com/osmart/hole2/issues/16).