How can you initialize chartboost for android?

How can you initialize Chartboost for android? I followed everything in the tutorial provided by Chart Boost but the SDK is still not initialized

Required permission: android.permission.INTERNET
Required permission: android. permission.ACCESS_NETWORK_STATE

repositories {
      maven { url "https://chartboostmobile.bintray.com/Chartboost" }
}

dependencies {
       implementation 'com.chartboost:chartboost-sdk:8.2.0'
}
        implementation 'com.google.android.gms:play-services-ads:19.5.0'
        implementation 'com.google.android.gms:play-services-base:17.5.0'
        implementation "com.google.android.gms:play-services-ads-identifier:17.0.0"
        implementation 'com.google.gms:google-services:4.3.4'
        apply plugin: 'com.google.gms.google-services'

<pre>

<activity android:name="com.chartboost.sdk.CBImpressionActivity"
               android:excludeFromRecents="true"
               android:hardwareAccelerated="true"
               android:theme="@android:style/Theme.Translucent.NoTitleBar.Fullscreen"
               android:configChanges="keyboardHidden|orientation|screenSize" />

import com.chartboost.sdk.Chartboost;
import com.chartboost.sdk.CBLocation;
import com.chartboost.sdk.ChartboostDelegate;

public static void startWithAppId(Context context, ​String appId, String appSignature){
}

Chartboost.showInterstitial(CBLocation.LOCATION_DEFAULT); 

-keep class com.chartboost.** { *; }