In the menu section, you can change, add, remove a menu. Also, you can able to set the Menu location (where you want to place the Menu). To customize your theme’s Menu you can follow the screenshot below.

From here, you will be able to choose which section you want to add to the Menu Section during customization.

Here, you can select your Menu (if your Menu is more than 1). Also, can change Menu item (Category, Posts, Portfolio, and Custom Link).