If you are using swift, first import the WebKit module in any files you're using web kit API:
import WebKit
Then you can use the web view:
let webView = WKWebView()
you need to import webkit in file
You should import the header #import <WebKit/WebKit.h>
#import <WebKit/WebKit.h>
and add WebKit.framework in Build Phases if you're using objective-c.
WebKit.framework