Hi Jennifer. Thanks for your question and the helpful link.
File uploads are not an easy or straightforward issue to tackle, due to write permissions, file type permissions, security concerns, size limitations, where to store the files (e.g. on server or also add to Media Library database).
As such, my guess is that it’d be easier to get a WordPress plugin that handles file uploads (e.g. Gravity Forms + Custom Post Types, Caldera Forms, Ninja Forms, etc.) and map the form submissions to the tribe_events custom post type, along with our plugins’ custom fields.
Please know that we cannot provide in-depth customizations, per our Scope of Support Terms, but you might be interested in contacting one of our known customizers. (We do not take such customization work.)
I hope this info helps!