If you need a book, Photoshop for Dummies or Photoshop for Beginners. If you need online, search on Google for paid or free information. I learned Photoshop years ago and I am glad I did. So good for you that you want to learn. Leilani
Now there are so many ways to learn PhS. Videos on YouTube, different courses, online trainings. If you want to learn this program quickly, self-study isn't a good idea.
+1 for Lynda.com, while Youtube may have the info you will have to sort through a bunch of less than helpful videos in the process. Whereas the instructors and information from Lynda are top notch. $$ well spent
lynda.com is great for tutorials, along with Youtube. I highly recommend the Photoshop Classroom in a Book by Adobe. While it won't cover everything, it will make you more well rounded than someone who just follows occasional YT videos.
Youtube for me was the best. You can learn anything there. Over the shoulder type tutorials are the best way to learn. if you fancy paying for a course thereare a few good ones on udemy and lynda.