Once you've opened a template, you can now make changes to it. You can change the font size, font color, etc. if you want, and you can also customize the data.
To edit the data, click on a cell. It then selects the cell, as shown below.


Now simply type the data you want.
We can also change the style of the template.
Notice below that we've clicked on the cell for Friday.


While the cell is selected, you can also click the Cell Styles button to see the style gallery.


You can modify the style to change the formatting.
Click on any item in a template, and you'll see a bounding box appear around it:


Word
You can then cut or copy it or even replace it with some other item, including an image.
If you want to change the look and feel of the tables used in the template, you can do that by selecting a table in the template, then using the Format as Table button.