Hi Ashish,
In terms of using GenerateBlocks, I would suggest watching this video as a guide on how to use it and create layouts of your preference: https://www.youtube.com/watch?v=R7fwJECtgSg
Now, once you’ve watched that, the demo site you linked seems to have the blog page as the homepage, and to alter its layout, using a Content Template – Block Element would be best, as recommended by Leo.
You would need a Grid Block with an Image Block on the left, and multiple Headline Blocks on the right column.