This documentation is not using the current rendering mechanism and is probably outdated. The extension maintainer should switch to the new system. Details on how to use the rendering mechanism can be found here.
There are two ways of installing the extension. Click here for more details: https://wiki.typo3.org/Composer#Composer_Mode
From TER (Classic Mode)¶
Select "Get Extensions" in the extension manager and update your extension list. Search for "px_validation" and click "Import and Install" to get the latest version. There are no other dependencies than TYPO3 6.2.
Please use the following command to get the extension from GIT.
git clone https://github.com/portrino/px_validation
Via Composer (Composer Mode)¶
Since TYPO3 7.x you are able to get extension via composer. As described on https://wiki.typo3.org/Composer#Composer_Mode you just have to use TYPO3 in Composer Mode
and add this line to your require section within the composer.json file and run
composer install and
If you want a specific version than change "dev-master" to the version you need.
Wether you run your TYPO3 in Classic Mode or Composer Mode you should install the extension via ExtensionManager or via Composer. Click here for more details