How to send an attachment with a form in html using Web3Forms

/Im using Web3Forms and the email sends,but the problem is that the attachment shows up as plain text and doesnt open./

 <form action="https://api.web3forms.com/submit" method="post">
            <input type="hidden" name="access_key" value="261987ac-8575-439e-8b44-14d9896905b8">
            <div class="form-group">
                <label for="firstName">Name <span>(required)</span></label>
                <div class="name-inputs">
                    <input type="text" id="firstName" name="firstName" placeholder="First Name" required>
                    <input type="text" id="lastName" name="lastName" placeholder="Last Name" required>
                </div>
            </div>
            <div class="form-group">
                <label for="email">Email <span>(required)</span></label>
                <input type="email" id="email" name="email" placeholder="Email" required>
            </div>
            <div class="form-group">
                <label for="subject">Something about yourself<span>(required)</span></label>
                <input type="text" id="Description" name="Description" placeholder="Description" required>
            </div>
            <div class="form-group">
                <label for="file">Upload your CV <span>(required)</span></label>
                <input type="file" id="myFile" name="filename">
            </div>
            <button type="submit">Send</button>
        </form>