1) Go to Administrator Links >> Blocks
2) Click on the "Add block" tab.
3) Enter the description, the block title (if one is desired) and the block body. In most cases, the input format should be set to "Full HTML".
4) Click "Save Block".
5) To make the block to appear (or not appear) on selected pages:
a) Find the block you created in the block listing (it will be in the last section titled "Disabled") and click on "configure" at the end of the row.
b) In the "Page specific visibility settings" section, check "Show on every page except the listed pages" or "Show on only the listed pages".
c) In the "Pages" section, enter the URL for the pages you would like to include exclude. For example, for http://www.yousite.org/about_the_union you would enter "about_the_union" (no quotes). To include or exclude the front page, enter '<front>' (no quotes).
6) Click "Save Block".
7) Find the block you created in the block listing (it will be in the last section titled "Disabled"). Select the desired placement of your block from the region section. If the block does not appear on the home page, a good choice is often "Right column".
8) By selecting a weight, you can control what order blocks will appear in within a given section of the page (or "region").
9) Click "Save Blocks"