Sitelinks refer to website links sometimes shown below some of Google's search results. These links are used are meant to help users navigate quickly to different locations on your site.
Coming directly from Google "At the moment, sitelinks are automated... If the structure of your site doesn't allow our algorithms to find good sitelinks, or we don't think that the sitelinks for your site are relevant for the user's query, we won't show them."
Basically this means directly inside Showit both you and the platform is not able to tell Google how to structure search results. Additionally, Google does not provide details on how to specifically create sitelinks as the process is automated by their search algorithm, however as long as you follow healthy SEO standards and structure your website in a way Google prefers, sitelinks can be generated for visitors.
An important factor to improving the potential for sitelinks is also making sure Google is aware of your website and it's content. This article has information on how to improve ranking and search presence: