Here is a quick step by step on how to block someone.
I am using @Tripod as my example user.... I would never block Tripod.....
First .... Click on your name in the top left of the screen. Second ..... Click on GENERAL under settings area
Third...... make sure that you have these two settings checked the way you would like them to be.
Fourth..... Find someone to block and then block them... To do this just click on their picture and you will be taken to their profile page.
Fifth.......Click the block button and this will add them to you list of blocked people.