Cannot use SciChart in Android Studio because of license.

[khadicha]

Hello everybody,
I'm new in Android Studio.
Recently, I get a trial license key for SciChart Android v2x. I read many times tutorial to set license(https://www.scichart.com/licensing-scichart-android/) but cannot activate my license. Because it is not written in which file should I put the licence code. So I tried to write it in my MainActivity.java file of my application like below:
"
public class MainActivity extends AppCompatActivity {

private AppBarConfiguration mAppBarConfiguration;

String license = ("<LicenseContract>\n" +
" <Customer>nnuni@mail.ru</Customer>\n" +
" <OrderId>Trial</OrderId>\n" +
" <LicenseCount>1</LicenseCount>\n" +
" <IsTrialLicense>true</IsTrialLicense>\n" +
" <SupportExpires>12/31/2019 00:00:00</SupportExpires>\n" +
" <ProductCode>SC-ANDROID-2D-ENTERPRISE-SRC</ProductCode>\n" +
" <KeyCode>28a24cba44.........038a6c</KeyCode>\n" +
"</LicenseContract>");
// Use Static method SciChartSurface.setRuntimeLicenseKey()
SciChartSurface.setRuntimeLicenseKey(license);

@override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
........................................................"
But it gives me the error <Cannot resolve symbol"setRuntimeLicenseKey">
Perhaphs it is because I did't intialise static SciChartSurface class. But I think it is built in class so I don't know how to do.
Second issue was I right to put this code in this MainActivity.Java class or Should I create new file for it.
If everybody has experience with setting SciChart license in Android Studio, please help me with real example.
Thanks in advance
Khadicha