You can choose to block other users by clicking the "…" button in the upper right corner of any post on the "Home" page and select “Block” from the pull-down menu. To unblock the user, select "Unblock" from the same pull-down menu.

You can also block other users by clicking the "Connect" button on the right side of the tab in their "Profile" page and select "Block" from the pull-down menu. To unblock the user, select "Unblock" from the same pull-down menu.