You'll need a source code editor to work in and write/run your code. If you're running Windows(like I am), Notepad ++ gets the job done. It'll let you run your code in Firefox, IE, Chrome, and Safari so you can make sure it's rendering properly.
Bootstrap is a great mobile first framework that allows you to build a responsive website. This means that your site will re-size to fit the viewing screen whether your user is on a tablet, laptop, or mobile phone. It's very popular, which means it's well documented, with plenty of resources that help you hit the ground running.
There will come a time, many times actually, where you will get stuck. You'll have a question and be in dire need of some expert advice to get your project out of the muck. That's when you'll turn to stack overflow. It's a community of professional and enthusiast programmers who just love to answer your development questions.