Since Remix is going to be run on the Archive of Our Own ("AO3") this year, everyone who participates will be required to have an account there. You don't have to archive any of your other stories there, but you must be a member to participate in Remix, and you must upload your remix there before you can post it anywhere else.
We're also going to be doing a test-run of the signup form sometime soon, so if you don't have an account, and you want to participate, now is a good time to get one.
Luckily for you, I have a bunch of invite codes, so if you drop me a comment with your email address, I will send you one.
Obviously, this offer is for people who are planning to participate in Remix this year.
- [admin] Archive of Our Own invite codes