How do you get there?

_{By completing the missions.}

which missions or the story mode missions?

The Story Mode Missions. You unlock it in the mission where you steal the trucks with Lance.

i just beat mission d.i.v.o.r.c.e is it almost going to open?

I don't think so. (I haven't played the game in a while)

d.i.v.o.r.c.e is pretty early on if I remember, that's one of the trailer park missions, i think you have to get onto the Lance strand.

D.I.V.O.R.C.E is the mission where you kill Marty, I'm pretty sure about that. If that's the case, you still have a while to go before unlocking the second island.

are you shuer

It opens after the mission, "From Zero to Hero". So you have a ways to go yet.