Envato has made a plugin you can use to help keep themes purchased from ThemeForest up to date.
You can download it from here. → https://envato.com/market-plugin/
(Envato is the company that owns and operates the ThemeForest website.)
If you need help with that plugin please ask Envato; it’s their plugin, not ours.
With regard to being new to WordPress, if you need to learn how to use WordPress then I can recommend the WordPress Lessons, they are a fantastic resource…
WordPress Lessons → https://codex.wordpress.org/WordPress_Lessons
If you can’t get on with the lessons and you need more help then you can ask questions in the appropriate WordPress support forum…
WordPress Support → https://wordpress.org/support/
Please keep in mind that we can’t teach you WordPress in this forum, you must go to the WordPress support forum or work through the WordPress Lessons.
In this forum we can help you only with issues that are directly related to the Vellum theme. To check if an issue is being caused by the Vellum theme, please switch temporarily to using a default WordPress theme, such as Twenty Nineteen for example. If the issue is still there then it means the issue isn’t being caused by the Vellum theme and so we can’t help with that issue.
If you need help with your GoDaddy managed WordPress hosting (which would include questions about FTP), please ask GoDaddy for support, we can’t help with that kind of thing in this forum.
Thanks.
P.S. Please allow up to 24 hours for any response from the support team, sometime longer at weekends and on public holidays.