Congrats on launching your venture.
First things first, what is your website about, and why should those different bloggers and journalists care? If you can answer this question (your elevator pitch), then you'll be off to a good start.
Secondly, you'll need to determine to whom you want to speak with and develop genuine relationships. Find out what the bloggers and journalists write about, what they like in life, what platforms they use, and more. Then start a genuine conversation so that you build up a rapport that way when you do email them to talk about your website, they'll be more receptive. From here you will learn more about the type of content they produce and if your product will be an organic fit for their readers. (Their contact information will also be somewhere online, and you'll also get a better sense of how you should write your pitch email.) Start with a small list of bloggers and journalists and then build up over time.
Thirdly -- what makes your website "newsworthy"? You can suggest this angle, but as you know, they're by no means obligated to covering your brand because it just launched. So again, make sure you understand WHY they should care -- and be able to articulate this reason concisely.
Furthermore, cold-calling is a no-no. Think about in your personal life. Most of us won't respond to emails or calls from people we don't know. And if there's attachments involved -- no way, we're downloading anything -- it could be SPAM or a virus.
Journalists and bloggers are very busy, and they are often working through hundreds of "requests for coverage" that come seemingly out of nowhere. Make their lives easier. Make your brand make sense for them. Make your message (and visuals) heartfelt. But most of all, be genuine. Since it's your website, I'm assuming you're passionate about the topic -- convey this through your messaging!
Hope this was helpful to you. I'd be happy to answer any questions you have here.