How do i obtain sitelinks in my search query on google SE?

You can only get addition/multiple links under the main link (in google search) if your website has rich content/higher traffic.

Google gives sitelinks ALGORITHMICALLY. They are judging the site based on quality, relevancy, etc. Then you could potentially get sitelinks. And once you have them, they are shown per query. So just because your website shows sitelinks for one query, doesn't mean it will for another. It's opaque and in Google's hands. You can help by building a really good website that is within their guidelines.