Hello Courtney,
The submit function should reset the form after every user as part of the process. But if that doesnt work you have another option the easiest is to just create a reset button so you or the audience can reset the form at any time after the submission. This would be coded like this.
<form action="url-to-formmail-provided-by-your-ISP" method="post">
First name: <input type="text" name="firstname" /> <br />
Surname: <input type="text" name="surname" /><br />
<input type="reset" value="Clear form" />
<input type="submit" value="Submit now" />
</form>
This would give you a submit and reset buttons.