How can I change the field box size in my contact form?

You can place a css class in the form content at the beginning (in the HTML section) like given below

<style type="text/css">
.input_custom_style
{
width:200px;
}
</style>

An image of this process is given below. While adding the code, please make sure that the quotes (“”)are correct. There is chances for getting different quotes while copy the code and paste it in your html section.

 

And then while configuring the form element give the ‘Style Class Name’ as input_custom_style

If you want a different width or style create such a css class.

In some cases, your default style may override the custom style. In such a condition, please use the code as

<style type="text/css">
.input_custom_style
{
width:200px !important;
}
</style>

Due to some features of wordpress, the style tag entered in the form section will disappear when saving it.

In such a situation, you can add the style in the style.css (default style) file of wordpress installation.