4
It's easy (if I understand your question correctly).
Open your administration control panel.
System Admin > Blocks
Scroll down to the Add a new block section.
Block type: Side block left
Weight: {this controls where this will be stacked within the other existing blocks int his area. Set this to a value between the weight of the Community Block, and the User Menu Block. Don't worry, play around with it a bit, you won't hurt anything.}
Visible In: {set what pages you would like to see this on. You can select multiple items by holding down the <shift> key while selecting}
Title: {What do you want to see for a title}
Content: {this is where you put your link, use HTML}
<a href="http://www.mysitename.com">Name of Link</a>
Like I said, play around with it.