I've followed online tutorials on how to create a table. When I add a table or row to my table, it just adds it to the side or bottom of the shape, making in larger instead of adding it WITHIN the table as i've seen online.
Once you have your desired number of columns and rows, you can resize the table by grabbing the lower-right corner.
Another option (that keeps your table size) is the choose a column, and select Split Cells Vertically to make one column into two, or choose a row and select Split Cells Horizontally to make one row into two.
You will get unevenly sized rows and columns across your table, but you can choose Distribute (Row or Column) Evenly to fix this.
Click on a row with the text tool. Go to Table menu > Insert Row. You'll then have the option to add a row above or below the row you clicked in. See screen shot below