Getting Started with the Map Viewer : Using the map viewer : Using the Layer Manager : Adjusting the opacity of the map
  
Adjusting the opacity of the map
1. Open the Layers Manager by selecting the Map Content and Legend button in the command bar.
2. If required, select the Layers tab in the Layer Manager.
3. Select next to the map service and from the menu that appears, select Opacity. The Transparency window appears.
 
Figure 15 
4. Move the slider to adjust the opacity. Move the slider to the left to increase transparency, and move the slider to the right to increase opaqueness.