Authorization header

I can’t get access to my API, I read, I need to create an authorization header, but I still get no access. What I do wrong, can someone help please, sitting long with this problem can’t continue my app building.

`iprivate fun sendRequestAndPrintResponse() {

    val url = "https://api.wanikani.com/v2/assignments?burned=true&subject_types=vocabulary&levels=1,2,3,4,5,6,7,8,9,10,11,12,13"

    val request = JsonObjectRequest(
        Request.Method.GET, url, null,
        Response.Listener<JSONObject> { response ->
            try {
                val jsonArray = response.getJSONArray("data")

                for (i in 0 until jsonArray.length()) {
                    val jsonObject = jsonArray.getJSONObject(i)

                    // Append character to textView here
                    val cha = jsonObject.getString("data")
                    //val burn = jsonObject.getString("user_specific")
                    //val burn2: Boolean = jsonObject.getBoolean("burned")


                    /*
                    * If the Kanji srs == burned
                    * Choose an random vocab
                    * Append to vocab variable
                    * */

                    val rand = chooseRandomVocab(cha)

                    vocab!!.append(rand.toString())

                    Log.i("myTag", "This is the kanji: $cha")

                }
            } catch (e: JSONException) {
                e.printStackTrace()
            }
        }, Response.ErrorListener { error -> error.printStackTrace() })

    getHeaders()
    mQueue!!.add(request)
}

@Throws(AuthFailureError::class)
fun getHeaders(): Map<String, String>? {
    val params: MutableMap<String, String> =
        HashMap()
    params["Authorization"] = "6c691219-b94e-4ea9-9f26-3cfe297b5516\t"
    return params
}`