Please follow the below mentioned steps to setup CometChat on your localhost:
Login to secure.cometchat.com using your CometChat Credentials.
search 'Web/Server Tech' and select your technology as per your requirement. Once select save it.
Now Click on 'Manage' Button. Now CometChat Cloud Admin panel open. Click on 'Install CometChat'.
Read instruction and add "Docked Layout" or "Embedded Layout" on your site as per your requirement.
Please find the attached screenshot of the same.