Dear Lord, why would you read the sparknotes for a book you are “only” reading for pleasure?
Read the book once through quickly. You can probably do it in a weekend. Make sure you have a good translation… the Bloom translation is very good. Don’t read the notes. Just read through it, and if you find your mind wandering, put it down for fifteen minutes and do something else.
That will give you a taste. If you want to understand it more deeply, limit yourself to a few pages per night. Puzzle over them. Ask yourself after each sentence “why would Plato put this here, and in this way?” Some people believe - and this is tough to swallow at first - that Plato wrote with logographic necessity. That is, everything that he wrote was intentional, and precisely placed. There are no extra words, no meaningless phrases, no fluff that isn’t important to understanding the work as a whole. Every action and circumstance (e.g., the dialogue beginning with Socrates coming back from a religious festival, and then being held against his will by the agents of a wealthy interlocutor) is planned and a necessary part of the whole.
When you ask yourself these questions, you won’t be able to answer many of them. Without a great education in classics, or indeed without having lived in Plato’s time, there will be some things that are simply impossible for you to know. But you will profit greatly from entering into a dialogue with Socrates and his companions, and posing questions back to them as they pose questions to you. Plato wrote dialogues instead of treatises for a reason.
And if you really want to learn more, read Alan Bloom’s excellent introductory essay to the text, and read some other secondary works by greats such as Seth Bernadete. Of course, you’ll have to read all of the dialogues to more completely appreciate what you read in one; that’s just how it works.
Sorry if this seems overly complicated, but Plato didn’t want it to be easy for you! Stretch yourself, push yourself! Philosophy isn’t without struggle.