I created a new site and added few basic components like Rich-Text and Image
I then followed below did below changes after reading few articles.
1) Duplicate Basic2 Theme with ExploreSXABasic2
2) Changed Theme in Settings - /sitecore/content/Tenants/exploresxa/Explore-SXA/Settings -- Compatible themes:
3) Selected Theme in Experience Editor -- ExploreSXABasic2
4) Export Theme
5) Edit index.html and component-richtext-content
6) Import Theme
But changes done in component-richtext-content are not imported.