This is likely due to CSS styling applied to standard HTML form elements within your current WordPress theme.
If you are "not comfortable with CSS" you would be best to select a WordPress theme that includes comprehensive CSS styling of standard HTML form elements. It's one of the key criteria we use when selecting a WordPress theme.
Alternatively to change the style of your CF7 forms you would need to edit the CSS style sheets used by your WordPress theme.
See Styling Contact Form for a general explanation of styling CF7 forms using CSS.
There is a link at the bottom of the page to a comprehensive and detailed article on Styling Contact Form 7 Forms. The article shows people, with suitable HTML & CSS skills, how to change the appearance of their Contact Form 7 Forms to meet their particular requirements.
