Many themes automatically display links to your pages in a top menu, but some themes (including Ryu) don't.
You can go to Appearance > Widgets and add the Pages widget to one of the "Top Widget Areas". This way you'll get automatic links to your pages, only they will be half-hidden. Check the theme demo:
If you add the Pages widget, the links will show in the black area that shows up when you click the first symbol in the top black strip.
Alternative: you can go to Appearance > Menus, create a custom menu, add your pages to it, and set it as your primary menu. In this case the links to your pages will show permanently in a horizontal menu beneath the blog title and tagline.
For more details on custom menus see this post of mine: