To jump start your website, just start writing. Your website is hidden from search engines at startup, so you are safe to experiment away. No one will see your edits until you make it live.
Even if you are intent on making a single page website, you may need to work out how to:
To open up the customizer, select from the top bar or Dashboard > Appearance > Customizer. The customizer provides a key route to modifying many of the website fundamentals, e.g.:
Switch template
Change colour scheme (template dependent)
Change fonts and font styles (template dependent)
Modify menus (you can do this also from the Dashboard > Appearance > Menus)
Modify Widgets (these are the marginalia like the sidebar and footer, if supported)
Adjust the front page settings
Add custom styles (for advanced users mainly)
Some templates will open up a raft of other options, sometimes a little bewildering so choose a simple template if this is your first time.
The customizer’s main feature is the ability to preview the changes on screen before you commit to them. Moreover you can save a draft of your changes, share that draft with colleagues, or abandon the changes altogether later if they are not approved. You can also schedule a change to go live at a later time or date.