I don't know whether or not this is on-topic... I have set up a Wix website so that I can have a forum for my HTML website, and I want the Wix website to be found on Google without paying for premium. How can I enable SEO without paying money?
Hope this answers your question.
"We guarantee that all of your site content can be crawled and indexed by search engines (e.g. Google and Bing) whether you have a Premium site or not." Referring Article
You mentioned wanting Wix for a contact form. Here are some alternative ways to get a contact form on your GitHub Page
Increase the page rank and SEO without paying for Wix.
Use the Wix Verification section to claim ownership.
Fill out the meta data for each page.
Give your images relevant descriptive names.
Use an online image compression tool to reduce the file size of your images before uploading.