Sounds like you got the "basic" fountain/syringe set up. What do you want from the enema, regarding, "doing the job"? There are enemas for different reasons, and they're not all the same as far as bag, and related attachments and their intended function. Again you have a basic set up. And regarding how far in the tubing goes, I think the packaging explains it. But again, it depends on what you want to achieve from these enemas. If the purchased item doesn't meet your needs, then I'd suggest you look on the web for enema equipment. One I'd recommend is the Optimal Health Network. A good amount of information, and a fairly large product line, going from inexpensive to pretty highly priced items.
A suggestion here too: If this will be your first trip into the use of enemas, start very slowly. If you know someone, say a nurse or other healthcare provider, you might talk with them. Same for a colonic therapist. They might not only advise you, but might administer the enemas.