.java

        //Fresco Image Loader
        OkHttpClient client = new OkHttpClient.Builder().addInterceptor(new Interceptor() {
            @Override
            public Response intercept(Chain chain) throws IOException {
                return chain.proceed(chain.request().newBuilder().addHeader("YOUR_KEY", "YOUR_VALUE").build());//here key and value are provided by the server
            }
        }).build();

        ImagePipelineConfig config = OkHttpImagePipelineConfigFactory
                .newBuilder(this, client)
                .build();
        Fresco.initialize(this, config);