Can someone help me with this Ranger story I'm making?

Just a suggestion, books featuring the military, Army Rangers no less, are usually written by reporters/authors embedded with those units or Rangers themselves. The best non-fictional/specific fiction books are always written by people with firsthand knowledge of the topic they are writing about. If you have no military history, you will find it very difficult to write about such a topic. You could try writing about a specific unit that does not exist at this time, where you can make up the rules as you go along. But writing about the Rangers specifically will be hard unless you know how a real Ranger would talk, act and conduct themselves.