Each theme has one to three menu options. You can manage these under the appearance theme and Menu tabs. Much depends on your theme itself as to how many menus you have. Your widget area is where you can designate what items to put in the sidebar verses the top or bottom portion of your site. When your menu shows a drop down it is because you have more than one item showing on that menu item. If you indent an item under another it causes the drop down effect. Your menu can contain a specific page, a specific category or a link to a form etc. I have an about page which has a drop down page which encompasses my media file. WP help menu will usually walk you through most things. There are also numerous help videos on YouTube which are immensely helpful and you can do a search to find the particular info you need.

If you go to word press you will see it has a help menu and you can find many things there also they have a help line

in the dashboard, go to appearance, then "customize". Then just look around and experiment with the settings without saving and publishing until you like what you've done. Each theme is different, so I can't give you any more than this without loading your theme myself.
Barry