There are a number of ways you can update your Reading Now.
Type the book you wish to add in the search window, select the book from the results by clicking on the cover and it will automatically be added to your Reading Now
Step 1. Go to your profile page and click on the + Add more books.
Step 2. Type the name of the book you wish to add in the search pane and select the book from the results by clicking on the cover.
Step 3. You will receive a confirmation once you have selected a book and the book will appear on your Reading Now.
You can also click on the See more... which will take you to your bookshelf where you can also add books to your Reading Now.
Visit the book page of the book you are reading by using search. Click on the Add to Shelf button, and select Reading Now to add the book to your Reading Now.