I know that conjuring a sentient being that is non-material is very difficult. There might be procedures, like rituals that invite that kind of being, which in itself requires practice, trial, and error. The concepts, though, are even more challenging. What is actually happening there. I assume it might be similar to a way a prayer works: opening a dimensional method of contact, maybe using concepts from physics like wormholes. Some beings, such as a water elemental, might be convinced to travel but not strong enough to with stand the trip; it would take a very serious and powerful practitioner of magic to convince a being powerful enough to withstand the trip to take the trip. Like convincing a king to come visit my apartment... It's only a dream. But if I were a powerful being, it would be more like the president inviting a king to The White House.
Getting it here is one part, staying in power once it is here is another trial. It is almost impossible to practice that. Maybe with astral projection it can be practiced, but that kind of practice session would still be immaterial.
I know I just need to take it slow, but even being in awe of such power, perhaps being a witness to, aide, or apprentice at such an event is just as enchanting as being the actual practitioner.