You need to apply for out alliance before the location is disclosed.
Apply for UG1
And then you will be given coordinates where you can land your castles.
I'm assuming your friends will be coming with you?
However, we won't give you the location yet, eve if you do apply. A lab castle is a currently upon us.
You can apply to join the alliance and later on, you'll be told where to land when it's safe.
It's the Killing Event you know?