Stastic is a website editor, so you will want to install it on a website, either one you already have or one we can create for you - check out the section “[Stastic installer: choose between “new website” and “existing website”]”
To install Stastic on a new or existing website, simply follow this link to Stastic installer. Then Stastic will copy its files to your website, in the /admin folder of your website, so you will have access to it at the address https://your-website.com/admin/ or if you do not have a custom domain and use the URL provided by github pages https://your-github-name.github.io/your-website-name/admin/