Although you can use the dialog box to set tabs. The easiest way to set them is from the Ruler bar.  If it is not visible, turn it on from the View menu. 

The default settings for tabs are a Left tab set every ½".  These tabs are represented by small gray vertical marks shown within the workable area of the document.

1.	First, decide what kind of tab you need.  By default the left tab is set on the ruler bar.   If it is what you need, just point to where you want it on you ruler bar.  The best place to point would be just above the light gray lines on the ruler bar.
2.	If a left tab is not what you need, point to the Left Tab button   on the tool bar.  Click the left mouse button until the appropriate tab set style.   You can choose from   Center , Right  , or Decimal Choose this link to see an example of what these tab styles do.
3.	Point to the desired location on the ruler bar.  Press the left mouse button.

If after you put your tab in your document and discover it is in the wrong spot, you can easily move it.  If more than one line of text is involved, choose the area first, otherwise only the line that your mouse is on will be effected by the change.

Point to the center of the tab set marker on the ruler bar.  It should be noted that if you do not point to the right spot on the marker, you will create another tab just beside the one you wanted to move.  

Point to the center of the tab set marker on the ruler bar.  Press the left mouse button and drag the marker down off the bar (a vertical dashed line will appear once you press the left mouse button to indicate you have click at the appropriate time). 

By the way, you don't have to pull down too far.  Just drag the mouse down until the arrow is back at the top of your document.

If you have set several tabs and are finished with them, you can choose to pull down each one individually or you can clear the bunch in one fell swoop.

From the Format menu, choose Tabs
Click on the Clear All button, then OK.

Presto, all gone.  Just like magic.