To download ArcGIS 10.6, you must access the website, as Esri does not provide direct public download links for this software. Official Download Process
Before you click download, ensure your hardware can run ArcGIS 10.6. Unlike ArcGIS Pro, 10.6 is for the ArcMap application, but it uses a 64-bit background geoprocessing engine. download arcgis 10.6
If you do not see the download option, contact your GIS administrator. They must grant you "Download" permissions within the My Esri portal. To download ArcGIS 10