Chantelle, I suggest you purchase this book. "The Art of Floral Design" by
Norah T. Hunter, I found it on Amazon used for about $100. I bought the earlier addition when I went to floral design school. Do you feel you have a solid foundation in the basics, flower name, care and handling, type of flower, i.e. line, mass, etc., elements of design and styles, This book is a handy reference.
Next do you have a talented designer that will challenge you, and give feed back on your designs, who will walk you through what is good and not so good about the designs you create. I found I needed another critical eye, because I loved any thing I was able to create.
Start simple, pick a design, even from the wire service book, and pick it apart in your mind, what is the structure, how do the flowers relate to each other, what is the proportion, what is pleasing about the color, and what in your eye would you change, once you have analyzed the arrangement, make your own, critique with the above designer, and do it again. Take your time to do the design, speed will come with experience.
When I took my classes, the critique was the most important part of learning how to design, I can still hear my instructor in my head as I design.