Try to play with the article, try to add another section (\section{}), another paragraph (separated by one or more blank lines).
Change the document class (\documentclass{}) to coursepaper and compile the article.
Observe how changing the document class affects the article composition.
Change the bibliography style (\bibliographystyle{}) to abbrv and then alpha. Notice how it changes the bibliography and references in the text. These are just some of the bibliography styles available.
Create a new text file (new.tex). Write any text in it. Add a line to the text in the clanok_en.tex file