If you want to creat a table in FCKeditor you must press the "Insert/Edit Table" 
button on the toolbar.
After that a popup window will apear (be sure to enable popups in your browser).
In the popup window you will find several field which you should fill in. Not all of the fields are required to build a new table.
Rows: in this field you specify how many rows do you want to have in your table .
Columns: in this field you specify how many columns do you want your table to have.
Border size: sets the thickness of the tabels border.
Aligment: specfies the alignment of your table. You can set it to left, center or right.
Width: sets the width of you table in pixels or percentage. E.g. if you choose 40 percnet the table will take 40% of the editings area width.
Cell spacing: specifies how thick will the cells border be.
Cell pading: sets the hight of the cell.
Caption: specifies the title of your table. The title will apear in the top of the table.
Summary: sets a comment on the table. The comment will not apear in the table. It is only for usage.