Start ioquake3, select "Mods" in the main menu, and activate CPMA.

Now you need to load up a map to play in. For most gametypes the best way to do this is through the "Practice" menu. However for "rocket arena" played on the multi-arena maps (ra3map*) it's probably better/easier to use some console commands.

For example you can run around in the multi-arena map ra3map1 as follows:
* Open the console (with the backtick key) and enter the command "\map ra3map1".
* Once you're in-game, press ESC and select "Choose Arena". You'll see a list of arenas. The small ones are marked DA ("duel arena") and the big one is marked CA ("clan arena").
* Select the small arena "Thunderstruck" and click the "Play" button.

Now you can poke around in here and see what it looks like. Duel arenas are really small and simple; this one is a good example.

To bring the game physics more into line with how our server will be set up, once you're in-game you can reopen the console and issue the command "\callvote gameplay vq3".

You can also try playing against an AI opponent:
* Press ESC and select "Add Bots".
* In the dialog that appears, click on Skill until some good-sounding skill level is selected.
* Click on one bot name (doesn't really matter which, you can leave the default "Anarki" selected if you like). Click the "Accept" button to add one bot, then ESC out of the menus back into gameplay. A rocket arena duel game should start.

You can do a similar thing to play a team game with/against AI on a larger "clan arena":
• Press ESC and select "Team". Choose to join the red or blue team.
• Press ESC and select "Add Bots". This menu now allows you to choose which team you're adding a bot to. Add n bots to the other team and n-1 bots to your own team. Usually n is 4 or 5.
• ESC out of the menus back into gameplay.

P.S. This process of playing "rocket arena" vs bots only works on ra3map1-ra3map13, not ra3map14-ra3map20, because of some additional needed files that I forgot to cram in there.