How to create a simple Web Map with ArcGIS REST API

Question

Following the instructions on this page Working with users, groups, and items—ArcGIS REST API: Users, groups, and content | ArcGIS for Developers and the Add Item documentation I was able build a POST request in POSTMAN to add a new item to the user.

After getting the token, when I try the POST request to add the web map I get this error

{"error":{"code":403,"messageCode":"GWM_0003","message":"You do not have permissions to access this resource or perform this operation.","details":[]}}

POSTMAN Request

This is the JSON that contain some simple Web Map data,

{
 "operationalLayers": [],
 "baseMap": {
 "baseMapLayers": [
 {
 "id": "defaultBasemap",
 "layerType": "ArcGISTiledMapServiceLayer",
 "url": "https://services.arcgisonline.com/ArcGIS/rest/services/World_Topo_Map/MapServer",
 "visibility": true,
 "opacity": 1,
 "title": "Topographic"
 }
 ],
 "title": "Topographic"
 },
 "spatialReference": {
 "wkid": 102100,
 "latestWkid": 3857
 },
 "authoringApp": "WebMapViewer",
 "authoringAppVersion": "5.4",
 "version": "2.11"
}

Answer 1

I was using the wrong access token.

I was using the access token I had for the app I was testing instead of the user's access token that I had to get with oauth2.

I'm leaving this here for future newbies.