I use the Ogham for divination. It can be difficult at first to learn to read the symbols because they are both similar and difficult. You might want to try using either the ogham cards or one of the sets of sticks that contain both the symbol and the name of the tree to help you learn. There is a kit called " The Celtic Tree Oracle " by Colin and Liz Murray that contains both a small book to help interpret the symbols and a deck of cards that is a good place to start.
There are a number of good books on the subject. I'd recommend the following:
"Ogam: Weaving Celtic Word Wisdom " by Erynn Rowan Laurie
" The Celtic Tree Mysteries " by Stephen Blamires
" Ogam: Celtic Oracle of the Trees " by Paul Rhys Mountfort
"The Book of Ogham " by Edred Thorsson