Then, now that your book is copyrighted, you are ready to find agents. You don't need one, but a lot of publishing houses won't accept query letters from anyone other than an agent. There are publishing houses that accept unsolicited manuscripts, but they aren't the best in my opinion. But it's your decision. The publishing house that published Harry Potter in the US does accept unsolicited manuscripts, if you're interested.
When a publisher says that they do not accept unsolicited manuscripts, that means they don't want you to send them any part of your manuscript to them. But you can send a query letter to them, but only if they say the exact words I just typed.
If they say that they do not accept unsolicited manuscripts or queries, that means they don't want you to send them anything. They want an agent to send it, they don't want the author of the book to send it to them.
They say this because they want another opinion other than yourself and your family and friends -- if you let them read it (I recommend you do let them read it so you can get opinions on it) -- they want a professional opinion from someone who's been in the field.
There are a few agencies out there that only accept material from already-published-authors. This is okay, just go back to Google and research agents that represent the genres that are the same as your book.