Ok Patrick. (if you speak french, tell me cause I'm ...)
So, step by step (in english...)
On the Tab EXTRA clic (on the bottom) Chose Language
When you return on the main window, clic
Engine/ Manage / Details
Select a Engine on the left list.
On this new window, clic on the tab BOOKS
On the little window Arena Engine Book,with the mini icone folder on the right, Search on your computer a book in .abk (normaly you have to put them in a folder Book in Arena main Folder)
Ok ? (I hope...)
Then : Open/Apply (on the bottom)/Start Engine (on the top)
Know, if you play with this engine, it will be OK.