What they said
Actually, I just joined the MBBA and the Live sims are a good way to get involved in a hurry. Of course, I joined few sims before the trade deadline so decisions needed to be made fast.
The one thing I noted is that you said that you didn't have any software. You might want to scout leagues for now because the upcoming release of OOTP5 means that many leagues will be making the switch.
Most leagues have message boards and websites so take a look and see exactly how things are done and if they suit your needs. Just because a league doesn't have an opening right this moment does not means that will be the same forever.