Nickiminaj,
Congratulations on trying to read the Bible. What translation are you reading? Some are easier to read than others. Also, Protestant translations usually leave out 7 Old Testament books.
Motivation has to come from within so other people can only give reasons to read it, not motivation. If you want to find out about Salvation history and how God loves and takes care of us, that is one reason.
At 15, reading the Bible is a large undertaking. It is not one book, but a whole library of different types of books; 73 books in all. One thing you might do is find a Bible study group at your church and go to it. They can guide you and provide help and explanations for the difficult parts.
Another way to get help, although more work, is to get a Bible study course. There are many of them available, on line and in book form, some free, some very expensive; and everything in between.
I would suggest going to your local parish and finding help there.
Good luck and God bless,
Patrick
AMDG