You can populate or modify the properties of a WMS service in ArcGIS Server Manager. To do so, follow these steps.
- Open Manager and log in. If you need help with this step, see the topic Logging in to Manager.
 - Click Services > Manage Services.
 - In the Manage Services module, locate your service and click Edit 
.  If you don't see your service in the list, it may be located within a subfolder under the Site (root) folder. - In the Edit module, click Capabilities.
 - In the capabilities list, click WMS and verify that WMS is enabled.
 - In the WMS Configuration list, choose Enter service properties below.
 - Populate or modify WMS service properties.
 - Click Save and Restart. The edits to your service are applied immediately.
 
See Available WMS service properties to learn more about setting WMS service properties.