To edit the default text block on your homepage when you install your shop, you need to configure a module called Custom Text Blocks.
To make your changes, click on the Modules menu, then on Modules and Services. Then click on the Installed Modules tab. To easily find the Custom Text module, just enter the two words 'custom' and 'text' in the search field and confirm to show the modules that meet the criteria entered, so the Custom Text Blocks module.
Once the module is displayed on the screen, click on the configure button to the right of your module to open the configuration window.
You can then enter the text you want and edit it using the editor bar above the text zone. There you will find all of the functions you would expect (bold, italic, underline, alignment, insert images, etc.). Once the text has been entered and formatted, just click on Save.