there's a couple articles on here that would help you, and would be beneficial to you to read.
how to cast a basic circle:
go to the east part of your circle, raise your power [writing] hand into the air, and call forth the watchtower of air [find or where a chant] then light the candle [if you're using one] point your hand at the ground and walk to the south [fire] candle, visualizing a white light connecting the candles. when you make it to the south point, raise your hand in the air, say a chant, light the candle, and move to the west [water] repeat, then to the north [earth] and finally back to the east. some people will go around the circle three times, visualizing the light to be sure they cast correctly. when you feel the circles cast [you should be able to feel it around you in some way. say the win's died down, or it's warmer] walk over to your alter, and light the spirit candle, say something like 'and now the circle is cast' [stomp your foot, or tap the ground, or whatever you feel is best] when you open the circle, thank the four watchtowers, and ground around the circle the other way, snuffing out [not blowing out] the candles.
How do I summon or focus energy?
there's various methods, the most common is through meditating. visualize a white light entering your body when you inhale, feel it pool inside your body. when you feel you've got enough energy, visualize it leaving your body and surrounding whatever you're doing. if it's a spell, visualize the candles glowing with energy, if you're casting a circle, visualize a thick glowing line in the ground connecting the four candles. [or rocks or whatever]
as i said, for more information, look into the articles, there's various methods to do all the things you're asking.