As a good measure install all updates to this CentOS 6 server. Before you continue further. This step is optional.
pgdg is the repo that postgresql can be downloaded and installed from. Here is where you download it from. Identify which version of rpm you want to download for installing PostgreSQL database server. Right now I am picking PostgreSQL 9.2 for CentOS [CentOS 6 – x86_64] as this is the latest version at this time. Now that we have identified which version we want to download, right click on that hyperlink and click "copy link address".