Fiction publishing is desperately difficult to break into.
I suggest the following:
Rigorously prepare the first two chapters of your book so they look well-produced. Make sure you have carefully spell-checked the writing (Nothing is more off-putting that reading a misspelt ungrammatical piece of writing). Prepare a synopsis giving an outline of the plot. This should not be too long.
Print them off and put into a neat folder or binder.
Get hold of a copy of "Writers and Artists Yearbook", and look for an agent or publisher who says that they will read and evaluate new material. Also look for one that specialises in the kind of book you have written [horror/children's/romance/thriller ....].
Send your sample with a brief covering letter asking them for their comments.
Do NOT under any circumstances pay anyone for doing this!
You may well get the brush-off, but you may also get friendly replies. Whatever happens, if you want to write, and are impelled to write, go on writing.
You could also try doing short pieces and offering them to local journals or newspapers.
In the meantime, if you have a problem in your writing, post it in the Writing and Editing forum for help.
Student or Learner