Beginning with spell casting is something that truly requires a solid foundation related with the most basic forms of magical work. When you get there, to the point you do know the basic forms and vital magical skills one has to develop in order to successfully cast or use some other types of magic, you will ease the process of familiarizing yourself with spell casting easily, which eases up the whole process of your castings.
The 'basics' generally introduce you to magic, which includes the area of spell casting, of course. So you need to get ready to your spell casting quest by having all the skills the basics teach you to develop, and all the vital experience and knowledge you need to know in order to successfully cast. When you get introduced, you can know how to do many different things with your energy and the skills you've gained and developed, including properly casting your spells.
So see the links I gave you on the button of the post, and gain as much skills, knowledge, education, experiences you may have with the most basic forms of the magical arts which will "open many other doors", as I always say.