WordPress codex has very detailed instructions on how to manage Menus. You’ll find them here.

Note: If you use our Demo Content, please, be aware that WordPress importer plugin doesn't copy theme settings, only content. So you need to set the Primary Navigation in Appearance > Menus to make it look like on our demo.

Menu-1

 

Navigation position setup

To set the position of your navigation (top and right spacing), please, follow to Theme settings > Appearance > Header.

Here's an example from Riviera theme menu settings.

Menu-2

Note: When use a Demo content, your menu is set automatically like on the demo site - the color is appropriate. Only navigation positioning is not.The settings can vary for different themes, so some of them may be missing.

Navigation fonts setup

Follow to Theme Settings > Appearance > Fonts > Navigation

Menu-3

and choose the color, fontname and size for all the navigation elements: item title, hover, dropdown, dropdown hover.
There's a font line height option as well, so you can control the vertical distance between item lines.
Don't forget to save changes.