Pro Sites Register Form + WPMUDEV Themes looks weird

Hi there.

I've installed ProSites and some Themes from WPMUDEV, but it seems like the style is broken and it looks weird. You can check this at http://cloudstore.pt/pro-site/

Am I doing something wrong? Is there any way I can fix this?

Also, I'd like to tweak Register Forms like https://edublogs.org/ are doing. What is the best way to do this kind of tweaks?

Thanks again for all the help.