How can i allow site visitors to import event from events module to their google calendar? Like if i provide a link they can click it to import the event to their google calendar.

In Events 6.2.0, in the module's Edit Settings (on the RSS/iCal tab), there's an ICAL URL at the bottom of the page. This isn't displayed anywhere in the Calendar (only in the settings), so you'll need to provide the address for visitors so they can subscribe to or download that file. For a single event, it would have to be clicking the ICS file for just that event, but it will only open whatever program is configured on the user's computer to open ICS files.

I don't think there's a way to automatically have an event that you click on get added to a user's Google calendar. You are simply creating an ICS file. Normally, the user's computer is configured for which application processes ICS file types and I don't think you can get a browser-based calendar to accept ICS links by default.

The user's can DOWNLOAD the ICS files that are link and then upload/import THOSE files into their Google calendars OR subscribe to an entire calendar as I indicated in my previous comment.