Keep them short to start with, despite any temptations to go long right away. Much depends on the technique you have used nail-less. Some no-nails have a slightly more in-curved fingertip, and if you add a nail to that you are likely to hook the string badly. The thing is to use the nail as a ramp to push the string down towards the fingerboard, and the presence of the nail will largely amplify the effect of whatever you are doing at present.
And when you are wondering about nail shaping there's always my nail shaping video!