why the form I add looks terrible

When I add a web form or checkout form they look ugly and very different as original, how can I make they look as original style.?

This is how they look now http://4xventas.iiyuu.com/membership-account/membership-checkout/?level=1 and this is how it should look like: https://thefittutor.com/account/membership-checkout/?level=6/ of course just the web form elements not the rest of the design.

Thanks