how to do descriptive programing in Testcomplete

if you mean descriptive programming as in using operations like findchildbyxpath(), or the more modern findElement() operations, you would want to look at 

https://support.smartbear.com/testcomplete/docs/reference/test-objects/members/page/findchildbyxpath-method-page-object.html

https://support.smartbear.com/testcomplete/docs/reference/test-objects/members/page/findelement-method-page-object.html

however, the strength in using TestComplete for test automation primarily comes from using the name mapping repository to store these object references, instead of using "descriptive programming". and at a certain level, you will still have to refer to the page objects above by their aliases (most likely). just my two cents