Multiple Forms and vertical layout in forms

Hi all,

this is the first time I use qt and I need some help.

I am using qt creator to do my GUI therefore my forms are in ui format. and all of my widgets is placed under various layouts governed by a main vertical layout.

I wanted to fullscreen my application and so I used showfullscreen. However I notice that my vertical layout box is still at the top left hand corner.
1) How can I place it in the middle of the screen?

I also encounter another problem. I have multiple forms.
2) How can I load another form when button of one form is clicked.

for example: i have 2 forms (f1,f2)
f1 button got clicked and f2 will be loaded while f1 is close.