fix(doc): Update readme.md (#788)

* Update readme.md

Co-authored-by: Denis Fadeev <[email protected]>

readme.md

@@ -26,15 +26,22 @@ EVM-compatibility.
   contains the source code for the Solidity smart contracts that implement the
   core functionality of ZetaChain.
 
-## Building the source code
-
+## Building the zetacored/zetaclientd binaries
+For the Athens 3 testnet, clone this repository, checkout the latest release tag, and type the following command to build the binaries:
 ```
-make install
+make install-testnet
 ```
+to build. 
 
 This command will install the `zetacoded` and `zetaclientd` binaries in your
 `$GOPATH/bin` directory.
 
+Verify that the version of the binaries match the release tag.  
+```
+zetacored version
+zetaclientd version
+```
+
 ## Making changes to the source code
 
 After making changes to any of the protocol buffer files, run the following