Increase image height on homepage to full screen when entering website and centre text on image overlay

Site URL: https://sealion-guitar-cn6h.squarespace.com/#/welcome%23/welcome

hi there,

I would like to increase the height of the homepage image so that it fills the full screen when entering the website. I tried normal adjust but it is maximum height now. I think we need css for it.

I would also like to move the text on the image to the center/middle of the image/page. And move it a little bit more to the downside of the image. 

password: Test1234

Thanks a lot.