mfw2010.gardenbanana.uk wrote:

We built a rear extension and once this was all completed, the garden is
now a disaster. No grass and rubble all over. I am clueless about
gardening, but very interested. I would like to clear this up myself and
regenerate grass.

Can someone advise how I do it (sorry for being daft).

Grass pretty much grows all by itself... your only problem is that
you're clueless and daft about physical labor.