just add it where you want it .. luckily u seem to have picked up a premodded source where the user classes have been spread out.
firstly add the new class to the constants list
Code:
define ('UC_PEASANT', 0);
define ('UC_USER', 10);
define ('UC_DJ', 20);
define ('UC_VIP', 30);
define ('UC_UPLOADER', 40);
define ('UC_MODERATOR', 50);
define ('UC_ADMINISTRATOR', 60);
define ('UC_SYSOP', 100);
and then look through the rest of global.php checking for anywhere else you need to define it .. one place you will definately need to define it is in the get_user_class_name function i think it is. Just look at the code thats already in those functions and copy it out for the new class obviously using
UC_DJ and the level
20 where applicable