How do you start them?
I met subject sixteen for the first time and was then put into DNA Sequence 1. Completed that, and was brought back to sixteen. When do the Desmond sequences actually start? Because going by the trophy list I thought it would be something like Desmond Sequence 1 > DNA Sequence 1 > Desmond Sequence 2 > DNA Sequence 2 and so on. But I can't yet go on the Desmond levels. I'm guessing you need to do a little more of Ezio's story before starting Desmond's?
Yes run up to them and it tells you. The first one is 5 animus shards which you will find lying about much like the feathers.
I did the first one yesterday. It's messed up lol.