When you insert a new table using the editor, by default the table is made to be transparent.

However, in order to make a table that isn't transparent transparent, here is what you have to do:

1) Right click anywhere in the table and click on "Table Properties".

2) When the table properties pop up window appears, you will see two tabs at the top ("General" and "Advanced"). Click on the "Advanced" tab.

3) The last two fields are labelled "Border color" and "Background color". Both of these fields need to be empty in order to make the table transparent. If you see any text in either of these fields, then delete it completely. Once both fields are empty, click the "Update" button at the bottom of the pop up window.

The pop up window will close and your table will be transparent. Click "Process Page Update" to save your work and you're done!