added howto section.

git-svn-id: https://plugins.svn.wordpress.org/onlywire-bookmark-share-button/trunk@856588 b8457f37-d9ea-0310-8a92-e5e31aec5664
added howto section.

git-svn-id: https://plugins.svn.wordpress.org/onlywire-bookmark-share-button/trunk@856589 b8457f37-d9ea-0310-8a92-e5e31aec5664