cyt,

 
>>We have installed a  single  domain license Cutechat and we need to know if it is possible to run a  Sample Demo in the same server and later add a new single domain license to it.

Yes. After you place the order, all you need to to is uploading your offical license file to your server.

You don't need to reinstall the application

>>do we have to set it up as you explain on your web site

It's not necessary to set it up as we describe.

For example, you can create your own database name or use the existing database. You can create a different virtual directory for your cute chat...

Hope it helps.

If not, please provide more information so we can help.