Download OneScriptWebservice.zip file from the URL contained in your welcome email from OneScript@DigitalTools.com
Unzip the OneScriptWebservice.zip file to where you want to install the webservice (usually this is called something like C:\Inetpub\wwwroot\OneScriptWebService)
Change the connection string in the web.config file to connect to your database. This will be something like one of the following:
Server=myServerAddress;Database=myDataBase;User Id=myUsername; Password=myPassword;
Create a new web application in IIS Manager that point to the webservice. If using Windows authentication disable all other authentication types. Otherwise allow Anonymous authentication.
Test the webserive setup by clicking the "browse" link from within IIS. Note the new URL to the webservice, it will be used by the OneScript clients.