Please install and activate Contact Form 7 plugin and then; (This is a free plugin and you can easily install with theme plugin installer.)

1-) Open “Contact Forms” menu from WordPress backend.
2-) Add new contact form.
3-) Copy below sample form and paste into your form textarea.

<label class="field-title contactNameField">Name <span>(required)</span></label>[text* your-name class:contactField]
<label class="field-title contactNameField">Email <span>(required)</span></label>[email* your-email class:contactField]
<label class="field-title contactNameField">Subject</label>[text your-subject class:contactField]
<label class="field-title contactNameField">Message<span>(required)</span></label>[textarea* your-message class:contactTextarea]
<div class="formSubmitButtonErrorsWrap">[submit class:buttonWrap class:button class:button-green class:contactSubmitButton "SUBMIT"]</div>