Your domain tasleembhanjee.com is already mapped to foodandlit.wordpress.com, so you don’t need to do anything else to get that part set up.
If you no longer want to keep the domain thesmartfoodie.com, you can let it expire and ignore the renewal notifications you’ll receive by email. You can read more about the domain expiry process here:
Keep in mind that if you let the domain thesmartfoodie.com expire, you will completely lose ownership of it. The domain will no longer bring folks to your site and someone else can register the domain and point it to their own site instead. If you still want the domain, you’ll need to renew it.
Just let me know if you need further help.