The search box is in the top right of the screen. Start typing in it and it will begin to suggest pages you might be looking for — you can click on one to go directly to that page. Alternatively, if you type in an page title and hit ↵ Enter, you will also be taken straight to that page.
If you type a word or phrase which isn't an article title and hit ↵ Enter, then it will take you to the full search page, which lists articles where your search term occurs. You can also reach this page by typing something into the search box, then clicking the "containing..." link at the bottom of the list of suggestions. For example you might do this if you wanted to search for occurrences of the word "Fish" across Wikipedia, rather than be taken straight to the article Fish.
The search page also allows you to search the different namespaces which we learnt about earlier. You can choose one of the preset options (Content pages, Multimedia, Help and Project pages, Everything) or you can choose Advanced which allows you to check the individual namespaces you wish to search in.
Redirects
Some pages on Wikipedia are redirects, they don't have any content of their own, but just send you on to another page. For example UK is a redirect to United Kingdom. So, if you type UK in the search box, it will take you directly to the article on the United Kingdom (There will also be a note below the article title saying "Redirected from UK").
To make a redirect, first create a new page. You can then either use the VisualEditor menu and then click Page settings to choose a destination page, or you can insert the Wiki Markup code: #REDIRECT [[Destination]]. However, it's discouraged to to create redirects from one namespace to another.
Shortcuts
Wikipedians often refer to internal Wikipedia pages by shortcut names to make typing quicker. The Wikipedia namespace prefix can also be abbreviated as WP:. These shortcut pages are just redirects to the target page.
For example, Wikipedia:Neutral point of view can be written as WP:NPOV to link to it, or typed into the search bar. Shortcuts to a page are usually listed in a box in the top right of that page.
