ERSDE is provided as an MSI package. For further information about the installation options you can read the installation chapter in the documentation which is downloadable separately (it is also provided within the installation package).
Enesys RS Data Extension will run in evaluation mode unless you have a valid license key. When run in evaluation mode, Enesys RS Data Extension has all the features available in the standard edition but will stop working after 30 days. On 64 bits server, you may need an evaluation key for running Enesys RS Data Extension in evaluation mode. Send an email to the support (address is available in the documentation) for requesting an evaluation key.
ERSDE version 3 can be installed side by side with version 2 so that you can start using it even if you are currently running version 2.