This link gives instructions for installing things like Tuareg (a useful emacs mode) and Merlin (advanced IDE features)
Installing Tuareg is pretty simple and will make your OCaml coding experience a lot nicer (though it's of course not necessary). Merlin is probably overkill unless you know what you're doing.
The following documentation may be particularly useful as you work on your assignments.
Style: Some students have asked for more clarity about how we've been assigning style points. Here's some info...
Compiler warnings lead to the biggest deduction -- we consistently take off points for these.
We also take off points for code that, in the judgment of the grader, is very hard to read, either because of poor formatting, lack of documentation (including lack of type annotations where they'd be useful), or departure from OCaml idiom. You can find OCaml style guides online (like this one or this one). There is not a specific style we recommend, but it is helpful to be internally consistent in your code.
See also the CS51 Resources web page for OCaml books, references, and tutorials.