AfterShock is not released yet, but you can test AfterShock on official AfterShock servers using openarena-0.8.1. To test AfterShock download openarena 0.8.1 here and unzip the archive. Download the unified zip archive here and unzip it into the openarena folder. Start openarena, open the Mods section and load the mod named aftershock. To connect to one of our official AfterShock servers, it is recommended to set "cl_allowdownload" to 1 using the ingame console..

If you have problems testing AfterShock or any questions, send an email to the AfterShock-support or you can ask in irc and someone will help you.