Energy is basically all around you, and throughout the entire universe, circulates the life energy. It exists not only as an energy field around every living thing, but also circulates through the earth, through the atmosphere around us and throughout nature. The flow of this energy connects everything that exists, and you, as a living being, are taking in this energy at every moment. Thus, you do not need to "summon" energy in order to use it, feel it, sense it or gather and manipulate your energy for magical working or any other reason.
When you do know that energy is always all around you, it's easy to understand that you just simply have to channel this energy in order to manipulate and / or work with it. You do not need any particular "spell" to "summon" it.
So now you know that you just have to learn and practice about that subject for a specific period of time, and again without the need to "summon" it.
Learn about channeling energy, energy manipulation and using.
Also, it is important to learn about grounding and centering in order to know about energy float, and channeling it. It's important to ground in preparation if you want to get a good flow: visualize something making you feel heavy or bound to the earth and try not to move until you feel pressure in your feet and legs and possibly all the way up to your root chakra if it's intense enough. In this subject grounding is important because it simply raises some energy to work with ( it also has other reasons and helpful things to offer, but it is not relevant for here currently).
So, you can raise and channel the energy (grounding is one method) which is around us - everywhere and anytime, but - you do not need to summon something that is already floating around you.