There are a few ways you could add your form to a WordPress website. However, it sounds like the person that created the form wasn't working with WordPress in mind. If you know how to grab the HTML code from the form, you may be able to add that to a page or post using the "Text" tab on the editor. You would also need to make sure you upload any associated files in the way the creator intended.
As far as uploading files go, you can use FTP or SFTP depending on the type of hosting you have. If you can provide more specific information about what you have, that may help others give you better guidance.
JesseW - GoDaddy | Community Manager | 24/7 support available at x.co/247support | Remember to choose a solution and give kudos.