If you wish to cast spells, you should study Wicca; and if possible join a "real" coven, not one on-line! But you will not learn in a few days; it takes years!
However, magic itself is all around you.Using magic is as natural as breathing.Scientists do it all the time; of course they don't call it magic, they say it is "research". But, magic it is!
Magic can, and does, change things, But it cannot turn somebody into a frog! Or anything else,such as a mermaid.
But magic is a very wide and complex subject. It will take a great deal of study. To begin, read all you can; learn to breathe properly; learn how to meditate. Study Nature itself. Study the animals, always remembering that you are also an animal.
So, begin at the beginning. You will not learn it overnight!