Finding the PDF is step one; using it correctly is step two. Here is a study plan:
The breaks these complex rules into 50+ lessons, making it accessible for self-study. Asan Sarf English Pdf
Search for a "text-searchable" or "retypeset" version. Some volunteers have remade the book using LaTeX or modern word processors for clarity. Finding the PDF is step one; using it correctly is step two
A complete English version of Asan Sarf is rare, but here are your best options: Finding the PDF is step one