You should have had an overall idea of where you wanted to take your story to start, then break that down into sections or arcs.
Then you take your arc and break it down further, and these would be your chapters.
It isn't how to get from A to B, but A to Z via b,c,d etc etc
So if you are floundering, think about what your overall goal you want to achieve with your book is. Take that info, and think, What major things do my characters need to do to achieve that?
Then you take one of those and break down what they need to achieve that. Then, you start writing.
You are not locked into this, this is more of a guideline than a rule... hell in one of my works I changed my direction 7 times in 50 chapters before I settled out a bit...
just keep writing you will get there.