When you first open Literarium it's going to look a little empty. You don't have any pieces recorded, and you haven't created any tasks or favourited any markets, which means that the system doesn't know much about you yet.
The timeline and market activity sections of the timeline aren't going to be very relevant to you to start with, but hopefully by the end of this overview you'll have something happening.
You can add new works here.
If you're a brand new writer...
...you should start entering in-progress or concept stage stories, things you want to write or have thought about writing. It'll be pretty quick to enter unfinished work, but having them in the system means Literarium can look at the kinds of genres and lengths you are intending to write in (eg. Science Fiction Novellas) which will help the Market Activity section recommend markets that meet those criteria.
If you're a writer with some completed works...
...you should start entering your finished pieces, so that you can begin to submit them to markets and make them start working for you. Just like concept and in-progress work, the Market Activity section looks at the genres and manuscript types to recommend markets that match the work that you produce.