To download audiobooks to your iOS device, open the iBooks app and go to the Featured tab. Then click on the audiobook and its price to buy and download the audiobook.
Steps

Step 1. Open the iBooks app
This white, open book icon with an orange background is located on the home screen.

Step 2. Click Collection
It's one of the tabs at the bottom of the screen.

Step 3. Click Audiobooks
This option is near the top of the screen.

Step 4. Find the required audiobook
To do this, use the tabs at the bottom of the screen:
- Click the Featured tab for new audiobooks and Apple-recommended books.
- Click the Top Charts tab to view the most popular books.
- Go to the Search tab if you are looking for a specific book - enter its title in the search bar.
- On each of the tabs, click Audiobooks at the top of the screen to view audiobooks only.

Step 5. Click on the title of the audiobook you want to download

Step 6. Click on the price button
It is located under the title of the book on the right side of the screen.

Step 7. Click Buy
You will be prompted for your Apple ID credentials if you are not already signed in

Step 8. Click Purchases
It's one of the tabs at the bottom of the screen.

Step 9. Click Audiobooks

Step 10. Click All Audiobooks
If you've bought a lot of audiobooks, you can use another menu, such as Recent Purchases, or search for a book by genre

Step 11. Click Download next to the title of the desired book
When the audiobook is downloaded to your device, you can listen to it; to do this, go to the My Books tab at the bottom of the screen, click All Books at the top of the screen, and then select Audiobooks.