Do you just show up and fight?
Never been in it myself
Eagler
I pop in there any time I see someone online in there just to see if I can help anyone or if anyone wants to practice. Sometimes if the MA map is boring, I do stupid stuff like an "air show" routine just to pass the time. If there's someone in there, just ask if they want to fight. No one takes actual damage, which helps because you can remerge or practice certain scenarios. For instance, last night after a few fights I asked Blixby to attack me from above so I can practice reversals.
I don't think people use it because you sometimes might have to ask someone to go in there with you, and there's no reward. And, besides...who wants to practice
Sorry for the longwinded reply. To answer your question, yes you can. Just ask or bring a friend