From the
OpenArena FAQ: ... The installation is nearly the same as in Q3A. Simply copy the .pk3 files (of the map/model/etc) to your OpenArena/baseoa/ directory* ...
When it´s
done simply start with: openarena +map spam or if you aren't
familiar with terminals, once started openarena, bring down the
console ( `-key for me ) and type "/map spam". With "/team s" you can join spectators. Bots are supported - i mean if desired, go to the menu (esc-key) and select "add bots"...
* Linux and the like: ~/.openarena/
Mac: ~/Library/Application Support/OpenArena/
Windows: %APPDATA%\OpenArena\
ps.: btw the idea is not all original. it's like the 3rd "kitchen" map i've ever encountered.