How do I go about making a map that has many islands?

[Steen]

I am trying to edit the world generator 'World details' to increase the likelihood of islands appearing when making a huge map, but I keep getting only 1 large island. How would I create a map that has many islands?

[Bryan]

I would use the manual with stamper for this. 
You could adjust the sea level and then try adjusting the stamp settings. 
I think the manual with stamper is going to get you a better result.