Report in at the appropriate tent (beside the main shaft). They have a whiteboard on which to write important details - how many in the party, contact number, expected route, expected time out etc... There is no one-way system or (as far as I know) restriction on number of parties doing certain entrances/exits. Just use common sense if you meet another party at rigged sections.
The CPC folks up there are always very friendly and helpful. You can even walk up in normal clothes, change up there and leave a bag with your dry stuff while you're underground. All very civilised... in a caving sense.
As for solo caving, there's absolutely nothing wrong with it... as long as you take the usual precautions, e.g. always take 2 completely independent sources of light, let someone responsible know your intended route, call-out time etc... To be honest, the winch meet is a great time to do solo trips. You will almost certainly bump into other parties down there for a nice chat, helpful advice etc... If you were so inclined, you may even find another party to tag along with.
Have fun.