There isn't a single answer to this question since it can depend on what e-book you're using and what grammar you need. However, here are a few general tips that may help:
-See if the e-book has a built-in grammar guide. Many e-books, especially ones designed for language learners, come with a grammar reference section that you can consult when needed.
-Check online for grammar guides specific to your e-book. A quick search should turn up any user-created guides that can help you with your specific e-book.
-Use a general grammar reference book or website. If you can't find anything specific to your e-book, a more general grammar guide can still be helpful. Just look up the topics you're having trouble with and see if you can find explanations and examples.