Most Numbers templates include tables, text, and images that you can use as a starting point for your own spreadsheets. You can use or customize the templates’ design features—fonts, colors, cell data formats, size and location of images and tables, and so on—and replace the data with your own.
Click the cell to select it, then enter your own content.
Double-click the text, then type your own.
When you’re finished, click outside the text.
Click 
in the lower-right corner of the placeholder image, then browse for an image.
Click the image you want.
You can also drag an image from your Mac to the placeholder image.
To change the part of the image that’s visible, resize the mask for the image.
To remove a placeholder entirely, select it, then press Delete on your keyboard.