If you have a ticket for one the those tracks, you can participate by heading over to their server on Discord.  Go to the 'choose-your-roles section' under General Server Info there for instructions.

PS  I'm just a player, not affiliated with BMG, so that's about all I know about it.  Getting excited!

What is the url for the General Server?  I'm just in the Community Server and it doesn't have any sections like that.

Did you click the green check box in the "getting started" section? IIRC, that is what opens up the other content.

The link is in our event text you get when you buy a ticket but anybody that missed it, wants to just stay up on all the various shows we are doing (almost 20 of them this year), or has general questions (that will get answered about 10 times faster and better there then here).

BMG Discord server at -  https://discord.gg/cda2rDW

I signed in at least. But I don't know ANY of the DMs, plus I presume they are all excellent, being on the EXP track. So I will just wait for more players to show up.

I am registered for the first two Spelljammer league adventures. Is there somewhere the pregen characters are posted so I can take a little time to figure out what I want to play?

Greetings! All the action for pre-mustering will happen over on the Discord as has been said. I'll be over there trying to get all the teams filled before the con opens it's doors. 
Any questions, feel free to ask me here or there (there is preferred).
 

Last call for pre-mustering.