You need 9 eye of enders because there are already 3 in eye of enders in the portal already. you can get eye of enders from killing enderman this is what they drop. The trick is to look at their feet as they will teleport if you don't. You are also going to need blaze rods as well which you can get from the nether be careful when getting these as it is easy to die in the nether.
This is also get you
Just use the guide below if you want the coordinates.