Update README.md

Author: bestander

README.md

@@ -4,6 +4,16 @@ This is a copy of [Boost](http://www.boost.org/) that is used to build React Nat
 
 You probably don't want to directly use this repository. Its sole purpose is to distribute the Boost code for building React Native.
 
+## To update
+
+React Native build tools expect specific folder structure.
+Run this command to get a .tar.gz file and upload it to Releases.
+
+```
+tar -cvzf boost_1_57_0.tar.gz boost_1_57_0/
+```
+
+
 ## License
 
 The Boost Software License 1.0 is included with this repository and its releases.