loadRequest: is an instance method, not a class method. You should be attempting to call this method with an instance of UIWebview as the receiver, not the class itself.
webviewInstance.loadRequest(NSURLRequest(URL: NSURL(string: "google.ca")!))
However, as @radex correctly points out below, you can also take advantage of currying to call the function like this:
UIWebView.loadRequest(webviewInstance)(NSURLRequest(URL: NSURL(string: "google.ca")!))
Swift 5
webviewInstance.load(NSURLRequest(url: NSURL(string: "google.ca")! as URL) as URLRequest)
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