How to insert a decorative line across the top of the page?

How to insert a decorative line across the top of the page? I am a novice on any office type program. Libre office seems really nice but, I can’t figure out how to make the functions of the pictured icons actually happen. Once I clicked on the “line” tool at the bottom an drew a line but, it was not level. I need a line that is absolutely level and perfect for a resume (actually I’d prefer a fun quirky resume but… :-). Thanks for all help n advice.

Hold down SHIFT while drawing the line. There are also other methods for inserting a horizontal rule.