The posted co-ordinates are for the location of the cache container, which is up a tree. The log book is inside the cache container. The cache container is locked and tied to a tree. To open the lock you will have to find the key. The key is to be found within 100 metres of the posted location. The key is up another tree. Your task is is to find the right key, unlock the container, sign the log book and then put everything back where you found it once done.
To foil the local lock picking geocachers who might wish to short circuit the process, I have taken advice of a local locksmith who has provided me a lock that ought to defeat them. Should you wish to try your luck in this manner then go ahead. I am confident you will not succeed.