Nicole: Question

I'm having a little bit of trouble. The ideas are all there in my head and I know exactly what I want to put into my first chapter, but I just can't seem to actually write it. I've written about 200 words, there's just something that's stopping me from writing and it's getting quite frustrating.

So, when you're writing, how do you start? With the first sentence, or just write and then go back and edit it? Do you plan it, if so, how much do you plan? I've been told that I should just write roughly because I can easily come back to it later and re-edit it, but I can't really do that either ;l. It's so frustratinggg.

- Nicole