give your body element height 100% (has no effect but is needed)
add a section and give it height 100%, it take up all the viewport whatever the browser size is
add a container and give it a name like .form-container. under typography, click on horizontal centering
place inside the container a div with your form inside it, give the div a name, and display inline-block, and a width and a height, of the size you want to form to be. it should be horizontally centered now.
now center the container (.form-container) vertically, give it position relative, then this exact 2 settings:
Note that it’s % values for both.
Now it looks like your example. Click on the devices button, starting by the tablet one, and adjust sizes andstyles for each, as desired.