Hi Padma,
You can go to the Google API Console from here https://console.developers.google.com/ then navigate to the API Manager > Credentials page. You should be able to create and manage your own API keys from here.
There is a more detailed guide from this page https://developers.google.com/maps/documentation/javascript/get-api-key but more related to scripting.
Hope this helps.
Kind regards,
Boney Sze