You can find samples of the test online. You can find prep packs on JobTestPrep.
LinkedIn users also have the opportunity to take a free MS Skills test to display on their profile, although this is just an informal assessment and might not reflect the most current questions.
If you fail, LinkedIn requires you to wait a certain amount of time before you can try again. This is not an easy test and it is good practice as it gives some insight as to the types of questions you might see on the Microsoft Skills Test and an indication of your proficiency with using Microsoft Word.