Personally, i think that we can do much better things by using this DLL, which is not possible within QCUtil object of UFT. I have used this dll with C#.net and the experience was much better then QCUtil object. Specially when we have ability to catch errors efficiently in other languages which is not avaiable in UFT.
What exactly are you trying to accomplish? Perhaps if you explain it to us in greater detail then we will be able to provide more complete and relevant answers.
If you want to connect to ALM through custom code, then you need to access the ALM Tools page and find the HP ALM Client Registration. That needs to be executed on the systems where your code runs. Then in your code you will need to add a reference to the OTAClient.dll