Step 1. Add dependency in Gradle

First, you have to add jitpack.io in your repo.

repositories {
    mavenCentral()
    maven {
        url = "https://jitpack.io"
    }
}

Second, you have to add this dependency.

dependencies {
    compileOnly "com.github.toxicity188:QuestAdder:master-SNAPSHOT"
}

And reload your Gradle.

Done!