Essentially: we're now in the nominations period. In order to be able to request a fandom/ship and a kink when signups open, you will need to nominate it (or someone else will need to have nominated it). A couple of days after nominations close, signups will then open.

You should be able to find all the info about the exchange in the rules post here and the nominations guidelines post you originally commented on! But if you have any questions once you've read through everything, please feel free to ask.