Some sites both of you will need to be verified individually, on others you can join as a couple. On the bottom of most sites' homepage you will find the links as to what is required to become a model and how to go about it.
Keep in mind that this wont help you with all those other things required to do well at it, you will need some time to plan/ research how to give yourself the best start.
When you are researching if this is for you both. I would recommend some additional things to consider beyond advice others offer specifically for you as a couple.
1. What if one of you is more popular, does better, gets more attention than the other? Imagine the scenario of just one of you getting off all session for example.
2. Camming is fun, but almost all of your customers will be men, are you both comfortable with that?
3. Couples on cam have some additional difficulties in performing. Camera angles is one, another is making communication between you into teamwork, this will be hard work as the novelty of camming wears off.
4. If you find that using two accounts is a better option, how will you do that?
There is nothing quite as hot as two beautiful women into each other, good lesbian couples are rarer than you may think. There is definitely opportunity out there for more good model couples.