How to align a login box to always be in the centre of a page

Trying to create a login page, inserted a container, row(inside), column(inside), display block(inside), form (inside). Now trying to align the form to always be in the centre of the page. I selected the column and tried to set the margin and padding under spacing to auto pulling the outermost left vertical bar but not getting what I require. What am I doing wrong? someone help.