In the header of your website, tap on "Title of this Website" to open the text editor and set your website's title (which appears on all pages).
Your website title should reflect the identity of your business/activity. It may include your business name, the title of the book you are writing, the name of the country you are traveling in and blogging about, etc.
Of course, you can complement your title with a couple of keywords related to your activity. For example, the place you live in, or the kind of website you are making.
Be careful: If you add too many keywords, readers won't be able to remember the title of your site, your website will lose its identity, and the header of your website will end up cluttered with words.
Try to find a good balance between the header picture and your site title. The feeling you create in this area is present on every page of your website.
You can change the color of the title (or set a colored strip) to make your title more legible.