For this you will want to focus on mediating and visualization. Meditating will help you awaken your higher self, where more of your magical energy is kept. you may also want to cleanse and strengthen all of your chakras (each aids a different part of you and your energy) especially your brow and crown chakra. You can find many articles on that here or online easily. You may also want to try gaining energy from the natural world around you, which you can do by sitting in a nice calm area of the outdoors and imagine/embrace the energies of the plants and earth flowing into you. there are also some cyrtsals that can help you, such as amythest and tigers eye, moonstone, and crystal quartz.
Meditation and visualization are very important, but it is also improtant to remember that you are always using energy. Your every thought, word and action uses energy. You just need to focus and develop control over it. Energy follows thought, breath and motion. So when you meditate and visualize you are developing your thought and focus to be able to use energy in a controled way. You can also start to practice things like Tai Chi, Chi Kung, yoga, aikido, etc. All of these are good for developing your energy manipulation. They all focus on coordinating the breath, movement and intention to direct energy the same way we do in magic with chanting, dance, ritual movement, etc. There are some good free Chi Kung programs out there. I recommend the Shibashi method. There is a link on my profile. It is easy to learn and very effective.