How to install realm as a gradle dependency?

I am completely new to realm. I want to use realm db in my android project. I have gone through the official Realm documentation. I need to set up realm in my android project. For that I have added the gradle dependancy as

    buildscript {
            repositories {
                     jcenter()
                         }
            dependencies {
                classpath "io.realm:realm-gradle-plugin:0.88.2"
           }
       }
 apply plugin: 'realm-android'

This is what they have given in documentation. But this doesn't work for me. It gives error saying Plugin with id 'realm-android' not found.

This is my build.gradle file

apply plugin: 'com.android.application'
apply plugin: 'realm-android'
android {
compileSdkVersion 23
buildToolsVersion "23.0.2"

defaultConfig {
    applicationId "com.db.realmsample"
    minSdkVersion 14
    targetSdkVersion 23
    versionCode 1
    versionName "1.0"
}
buildTypes {
    release {
        minifyEnabled false
        proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
    }
}
buildscript {
    repositories {
        jcenter()
    }
    dependencies {
        classpath "io.realm:realm-gradle-plugin:0.88.2"
    }
  }

 }

 dependencies {
  compile fileTree(dir: 'libs', include: ['*.jar'])
  testCompile 'junit:junit:4.12'
  compile 'com.android.support:appcompat-v7:23.2.1'
  }

Is my configuration correct?