For gradle below 8

build.gradle

afterEvaluate {
    publishing {
        publications {
            // Creates a Maven publication called "release".
            release(MavenPublication) {
                from components.release
                setGroupId groupId
                setArtifactId artifactId
                version android.defaultConfig.versionName
            }
        }
        repositories {
            maven {
                url "http://127.0.0.1:8081/repository/maven-releases/"  //use the url what you've copied in nexus bashboard repository
                credentials {
                    //here your nexus username and password will be used
                    username = 'admin'
                    password = '<your_nexus_password>'
                }
                allowInsecureProtocol = true  // remove this line if you are using https:// instead of http://
            }
        }
    }
}