build instructions
diff --git a/README.md b/README.md
index 5c70b5e..6f327c1 100644
--- a/README.md
+++ b/README.md
@@ -1,4 +1,4 @@
-Module for PostgreSQL to support approximate algorithms based on the Datasketches core library datasketches-cpp.
+Extension for PostgreSQL to support approximate algorithms based on the Datasketches core library datasketches-cpp.
See [Datasketches documentation](https://datasketches.github.io/) for details.
This module currently supports the following sketches:
@@ -9,6 +9,34 @@
- KLL float quantiles sketch - for estimating distributions: quantile, rank, PMF (histogram), CDF
- Frequent strings sketch - capture the heaviest items (strings) by count or by some other weight
+<h1>How to build and install</h1>
+
+This code is intended to be distributed as a PostgreSQL extension on [PGXN site](https::/pgxn.org/)
+
+This code is expected to be compatible with PostgreSQL versions 9.4 and higher. It was tested with REL_11_STABLE branch.
+PostreSQL must be installed to compile the extension. The path to PostgreSQL executables must be set up (try running 'pg_config' to test).
+
+This code requires C++11. It was tested with GCC 4.8.5 (standard in RedHat at the time of this writing), GCC 8.2.0, GCC 9.2.0, Apple LLVM version 10.0.1 (clang-1001.0.46.4) and version 11.0.0 (clang-1100.0.33.8).
+
+<h2>Building and installing PGXN extension</h2>
+
+ - Download the datasketches extension from [PGXN](https://pgxn.org/dist/datasketches/)
+ - Unzip the package (the core library datasketches-cpp is included)
+ - make
+ - sudo make install
+ - in the database console: create extension datasketches;
+
+<h2>Building and installing from source</h2>
+
+ - Clone or download from GitHub, or download from Apache archive this datasketches-postgresql code and the core library datasketches-cpp
+ - Place the core library as a subdirectory (or a link to it) inside of the datasketches-postgresql like so:
+ - datasketches-cpp
+ - datasketches-postgresql
+ - datasketches-cpp -> ../datasketches-cpp
+ - make
+ - sudo make install
+ - in the database console: create extension datasketches;
+
<h1>Examples</h1>
<h2>Distinct counting with CPC sketch</h2>
